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The Future of Lasers

You could be forgiven for thinking physicists are obsessed with monumental architecture. Although their investigations often involve objects at the subatomic scale, the machines they use can be enormous. In 2008, for instance, construction work finished on the Large Hadron Collider (LHC), straddling the Swiss-French border. Sometimes described as the world’s largest machine , the LHC is a 27-kilometer-long circular accelerator that cost several billions. Already there is talk of building even larger particle accelerators. Early in 2019, some of the physicists who helped build the LHC floated the idea of a new circular accelerator 100 kilometers long .

But there is now a new kind of scientific machine on the horizon: a trimmed down particle accelerator that is small enough to fit on a tabletop. Diminutive they may be, but these table-top accelerators are still bursting with the power and versatility scientists demand to perform cutting-edge research. Already they have helped physicists better understand the 3D-printed metal components that could one day be used in aircraft manufacturing, and experiment with a new and improved way to hunt for cancer tumors. What’s more, the table-top devices should be so cheap to build that many universities may ultimately possess one. This means accelerator technology that is currently beyond the reach of many researchers may soon be far more widely available, which has the potential to speed up the pace of scientific investigation.

Developing these new tiny accelerators is a global endeavor, but researchers at U-M have made a particularly significant contribution. Some of the key technological breakthroughs that are paving the way for the new machines involve advances in laser technology that were made by past and present researchers in the College of Engineering – including a 2018 Nobel laureate .

Table-top physics

Over the last century, particle accelerators have become among the most important instruments in the scientific toolkit. It’s vast accelerators like the LHC, where subatomic particles are smashed together, that often grab the headlines. But in many accelerators, the idea is to manipulate fast-moving particles without colliding them – a process that can generate beams of intense X-ray radiation. Those X-ray beams have many uses. They have proved their worth in pharmaceutical drug discovery , in semiconductor research , and even in fossil analysis: X-ray beams can help identify the remains of ancient pigment molecules and reveal the original color of long-extinct animals .

“If we could afford it, there would be [X-ray-generating accelerators] in every university,” says Zulfikar Najmudin, a Professor of Physics at Imperial College London, UK. “But it’s just not possible because they are very expensive.”

Typically, an X-ray-generating accelerator costs hundreds of millions of dollars to build and, once complete, occupies an area the size of several football fields. Both factors make investing in an accelerator impractical for most universities.

An unfortunate consequence of this is that the accelerators are also beyond the reach of most scientists. There are just too few of the costly machines worldwide to meet the demands of modern research, meaning many scientists performing important work can wait years to obtain access .

Alexander Thomas gives an example. Thomas is a U-M associate professor of Nuclear Engineering and Radiological Sciences (NERS) in the Center for Ultrafast Optical Science (CUOS), as well as an associate professor of Electrical and Computer Engineering (ECE) and an associate professor of physics. He says additive manufacturing, also known as 3D printing, is becoming an increasingly important technology. “We’re to the point now that you can 3D print metals, and print components for aircraft,” he says. But tiny imperfections in the printing process could reduce the strength of those critical components. “You really don’t want these pieces to fail.”

One way to assess the quality of 3D printed parts is to probe them with the X-ray beams generated by an accelerator. But it’s difficult to secure access to those accelerators for this kind of fundamental research. What’s needed is a cheaper – and therefore more plentiful and available – form of accelerator. It’s this gap in the market that could be plugged by table-top accelerators. Using early versions of the table-top technology at CUOS and in the UK, Thomas is already collaborating with material scientists to investigate the internal structure of 3D-printed parts and identify imperfections that will help the researchers work out how to finesse the printing process.

Given how useful table-top accelerators promise to be, it’s perhaps worth asking why they are still in the development stage, while larger accelerators have been operational for decades. The reason is that the smaller versions of the technology operate in a completely different way than their larger counterparts.

A traditional particle accelerator uses powerful magnets to gradually ramp up the speed of subatomic particles – typically negatively charged electrons – as they travel through a ring-shaped vacuum chamber that is often hundreds of meters long . The miniature version effectively replaces this large, circular race track with a drag strip measuring just a few tens of centimeters in length. Over that short distance, electrons are accelerated at a far higher rate. That acceleration process is triggered by astonishingly brief and intense laser pulses. This means it has only become possible to think about table-top accelerators because of advances in laser technology.

Ultrafast science

The first working laser was demonstrated in 1960 . Within a few years, physicists had discovered that their lasers could be used to generate exceptionally short pulses of light, each lasting just a few trillionths of a second (or a few picoseconds) . “At the time there maybe wasn’t a technological reason for making those short pulses,” says Karl Krushelnick, director of CUOS and, like Thomas, a professor of NERS, ECE and physics. “ There was just an interest in seeing what you could do with lasers.”

As the years passed, physicists realized those short laser pulses could prove useful, but only if the researchers could find ways to increase their brightness (or intensity). Light has both electrical and magnetic properties, and so if a very brief flash of laser light is bright enough, it can generate a powerful electric field that will interact with any electrons in its path.

Unfortunately, generating short laser pulses of the required brightness had the potential to damage the laser equipment. In the mid-1980s, Gérard Mourou and Donna Strickland, working at the University of Rochester, developed a solution to this problem. Their method, Chirped Pulse Amplification , involved taking the short laser pulses and stretching them out in time, effectively diluting them so their brightness could be increased without damaging the hardware. Once boosted, the laser pulses were compressed again to give a very short – and now also very bright – laser pulse.

Within a few years, the researchers had refined the technology so it was possible to generate ultrashort pulses with intensities measuring 10 18 watts per square centimeter . That’s the e quivalent of many thousand times the output of all the world’s electricity power plants squeezed into an area one-quarter the size of a typical postage stamp. The research was so important it earned Mourou and Strickland a share in the 2018 Nobel Prize in Physics .

“We proved that we could increase laser intensity by orders of magnitude,” Strickland explained in a post on the Conversation, describing how she built the laser as Mourou’s graduate student.  “In fact, CPA led to the most intense laser pulses ever recorded.”

Mourou moved to U-M in 1988 – a decision he made because of the university’s strong reputation. “U-M was very big in optics even in the 1960s,” he says. Mourou then helped secure a prestigious National Science Foundation grant to establish CUOS. During Mourou’s time at Michigan, U-M’s international reputation for ultrafast optics research grew. Several commercial companies had their roots in CUOS, including Intralase – a firm that used laser pulse technology to develop a virtual scalpel for vision-correction eye surgery .

But arguably, the culmination of Mourou’s work at U-M was the construction of the HERCULES laser system in the late 90s and early 2000s. Harnessing Chirped Pulse Amplification, HERCULES was, by 2004, producing 45 terawatt pulses of laser light with a world-record intensity of 10 22 watts per square centimeter . It is lasers such as U-M’s HERCULES – and a similar UK laser facility called Astra Gemini – that power the table-top accelerator experiments now being conducted by Thomas, Krushelnick and Najmudin.

Taming the table-top beams

Before table-top accelerators became a genuine possibility, though, there was one more hurdle to overcome. By the early 2000s, physicists could use lasers like HERCULES to accelerate electrons to high speeds over very short distances. But those speedy electrons tended to shoot off in all directions. Physicists needed to tame them – corral them into narrow beams in which all of the electrons travelled along the same path at the same energy.

By 2002, researchers including Krushelnick, Najmudin and Stuart Mangles, a Reader in plasma physics at Imperial College London, had worked out how to encourage the electrons to form tight beams , but the electrons within those beams still carried different energies. “They were ugly beams,” says Thomas.

Then, in 2004, Mangles, Krushelnick, Thomas and Najmudin helped overcome this stumbling block. They were members of one of three research teams that independently worked out how to guarantee the electrons in the beams all carried the same energy . The research, which was conducted using the Astra Gemini laser in the UK, was such a significant step in the development of table-top accelerators that it made the cover of the prestigious Nature scientific journal.

“Those studies were truly enabling,” says Gianluca Sarri, a Reader in the School of Mathematics and Physics at Queen’s University Belfast, UK, who now collaborates with Krushelnick, Thomas and Najmudin.

Back in 2004, Krushelnick and Thomas were based at Imperial College London, but a few years later they both moved to U-M. The HERCULES laser was a major factor in that decision, says Thomas. “It’s not just that it has such a high intensity,” he says. “It’s having a laser of that scale in a university setting – that’s quite unique.”

Over the last decade, the researchers have begun putting their laser-powered table-top accelerators to work, addressing fundamental questions at the cutting edge of science. It’s research that has taken them on a virtual voyage into the core of violent explosions occurring in galaxies far, far away.

Signals from space

During the Cold War, suspicions were high that parties who had signed up to the 1963 Partial Nuclear Test Ban Treaty might attempt to break the agreement and conduct clandestine nuclear weapons tests in space, perhaps on the far side of the moon where they would be out of sight of Earth-based observers . United States authorities launched satellites in the 1960s and 70s to monitor for the gamma rays that the explosions would generate. In the late 1960s, the satellites began detecting such signals. They were not coming from behind the moon, however: they originated from deep space.

The earliest media reports speculated that these “gamma ray bursts” might be evidence of battles being fought between powerful alien civilizations in distant galaxies. As recently as the 1990s, some astronomers were suggesting that gamma ray bursts might be some sort of alien communication system .

“It’s actually not something to be taken too lightly,” says Sarri. “We do constantly receive a lot of signals from outer space. You have to try to catalogue them all and find a natural reason for them, so you can rule out that they are not alien transmissions.”

The consensus view today is that gamma ray bursts are nothing to do with extraterrestrials. But to really confirm the idea, astrophysicists need to know that their theoretical models for how the bursts form match with reality. This is where the table-top accelerators in Michigan and the UK enter the story. Using them, a team including Sarri, Krushelnick, Mangles, Najmudin and Thomas essentially generated mini-gamma ray bursts in the laboratory . Their research strongly suggests that at least some of the gamma-ray bursts that have been puzzling scientists since the 1960s stem ultimately from the behavior of black holes. “We now have other experiments lined up to probe the physics in more detail,” says Sarri.

The gamma ray burst experiments are an example of how the high-speed electrons from a table-top accelerator can be put to work. But in conventional accelerators it’s the X-rays these electron beams can produce that are arguably even more useful. It turns out that table-top accelerators can generate X-ray beams too, and they could transform healthcare.

‘Free’ X-ray beams

When electrons are moving at high speed, any sudden changing in their direction of travel generates a bright beam of X-rays. Often, physicists use a special piece of hardware – a device they call a “wiggler” – to induce this direction change. With a table-top accelerator, however, the wiggler comes already included. Najmudin, Krushelnick, Thomas, Mangles and their colleagues discovered that when their laser pulses accelerate electrons, the particles are violently shaken at the same time. In other words, the electrons suddenly changes their direction of travel, which means they fire out an X-ray beam. “And the X-ray beam is actually really high quality,” says Najmudin.

It’s these X-ray beams that Thomas is now using to probe the internal structure of 3D printed materials that might eventually be used in aircraft manufacture. But the X-ray beams have other applications too. “We’re very interested in imaging tumors,” says Najmudin.

Already, doctors use low-energy X-ray beams to produce mammograms and search for breast cancers. But mammogram images are relatively fuzzy and poor quality. “It’s a real skill to be able to identify tumors, and there is a problem of false diagnosis,” says Najmudin. The higher quality X-rays generated by laser systems can generate sharper, better images.

This is because, using those higher quality X-rays, it’s possible to focus on phase contrast – the subtle but detectable way that X-rays change direction as they move through body tissues of slightly different compositions. In 2018, Najmudin and Mangles and their colleagues showed how this “phase-contrast imaging” could produce exquisite images of the different tissue types in a 1-centimeter-long mouse embryo. The same technique could one day make it easier to detect breast cancer tumors when they are still just a few millimeters wide rather than having to wait for them to grow to centimeter-widths. “That is probably one of the most exciting things we can now apply our research to,” says Najmudin.

The future of lasers

Already, table-top accelerators are beginning to transform science. By boosting the power and intensity of the HERCULES-style lasers that drive the machines, even more will be possible. For instance, Najmudin points out that more energetic laser systems will be able to produce X-ray beams with enough energy to scan for tumors inside living people instead of just within tiny tissue samples.

As such, many eyes are now focused on the Extreme Light Infrastructure (ELI), a European project initiated by Mourou in 2006. Earlier this year, the ELI-NP laser facility in Romania began producing 10-petawatt (10 million billion watt) laser pulses that will ultimately be capable of intensities of 10 23 watts per square centimeter – some ten times more intense even than HERCULES can presently muster.

Mourou – now a Professor and Member of the High College at Ecole Polytechnique in Paris, France – expects ELI-NP’s laser pulses will prove to be a powerful new tool for exploring the subatomic world. He also anticipates exciting future laser applications beyond the table-top. For instance, laser pulses could help change the trajectory of pieces of space junk in Earth’s orbit , sending them into the atmosphere to burn up. Mourou also thinks that laser pulses could help “transmute” nuclear waste – literally changing the chemical elements it contains into different elements so that instead of remaining dangerously radioactive for thousands of years the waste becomes safe in a matter of minutes .

Exciting though these European-led projects and proposals are, they also highlight that North America has lost ground at the cutting edge of laser research. “At one point all the highest intensity lasers were based in the U.S., but the past 10 or 15 years have seen a shift to Europe and to Asia,” says Krushelnick.

But there are promising signs that U.S. authorities want to reverse that trend. A 2018 report by the National Academies of Sciences, Engineering and Medicine recommended the Department of Energy consider building new laser facilities to rival those now being constructed in Europe and Asia. “Hopefully we might even leapfrog those facilities,” says Krushelnick.

There are reasons for near-term optimism too. In September 2019, the university announced an upgrade: with $16 million from the National Science Foundation, the work will soon begin on a major overhaul of the HERCULES laser system that will see it capable of producing 3-petawatt laser pulses. “That’s a factor of 30 increase in laser power and intensity over what we’ve had before, which puts us in the regime where we are able to produce antimatter from the laser beam interaction,” says Thomas. (See “Boiling the vacuum.”)

In this new upgraded form, HERCULES will be renamed ZEUS, and it should have a big impact on the continued development of table-top accelerator research at U-M. Mourou – who was instrumental in the initial construction of HERCULES – welcomes the developments. “I still keep in touch with [the CUOS researchers] and I’m extremely interested in seeing their progress,” he says.

As significantly, 2018 saw the establishment of LaserNetUS , a network that will help optics researchers across the U.S. form stronger collaborations and improve access to the HERCULES laser and the table-top particle accelerator experiments it allows. “It supports the running of these lasers to get the most out of them, and it’s also about building a community,” says Thomas. With LaserNetUS, and the NSF investment in the HERCULES/ZEUS laser, there is now a bright future for laser technology – and table-top accelerator research – across the U.S.

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OP-TEC: Course Materials

Downloadable curricular materials developed by the National Center for Optics and Photonics Education (OP-TEC) designed to support optics, laser, and photonics education in high schools and two-year colleges, and the retraining of adult workers.

Laser Optics & Photonics Series

Course 1: Fundamentals of Light and Lasers, 3rd Edition

Module 1-1: Nature and Properties of Light Module 1-2: Optical Handling and Positioning Module 1-3: Light Sources and Laser Safety Module 1-4: Basic Geometrical Optics Module 1-5: Basic Physical Optics Module 1-6: Principles of Lasers

Author(s):  OP-TEC: National Center for Optics and Photonics Education

ISBN:  978-0-9998536-4-1

Publisher:  OP-TEC

Year:  2018

Category:  General Optics & Photonics

Recommended Grade Level:  College – 2nd year

Support Files:

PDF: FLL_Figures_and_Images_for_Instructors_Module_1-1_Nature_and_Properties_of_Light_3rd_Ed PPT: FLL_Figures_and_Images_for_Instructors_Module_1-1_Nature_and_Properties_of_Light_3rd_Ed PDF: FLL_Figures_and_Images_for_Instructors_Module_1-2_Optical_Handling_and_Positioning_3rd_Ed PPT: FLL_Figures_and_Images_for_Instructors_Module_1-2_Optical_Handling_and_Positioning_3rd_Ed PDF: FLL_Figures_and_Images_for_Instructors_Module_1-3_Light_Sources_and_Laser_Safety_3rd_Ed PPT: FLL_Figures_and_Images_for_Instructors_Module_1-3_Light_Sources_and_Laser_Safety_3rd_Ed PDF: FLL_Figures_and_Images_for_Instructors_Module_1-4_Basic_Geometrical_Optics_3rd_Ed PPT: FLL_Figures_and_Images_for_Instructors_Module_1-4_Basic_Geometrical_Optics_3rd_Ed PDF: FLL_Figures_and_Images_for_Instructors_Module_1-5_Basic_Physical_Optics_3rd_Ed PPT: FLL_Figures_and_Images_for_Instructors_Module_1-5_Basic_Physical_Optics_3rd_Ed PDF: FLL_Figures_and_Images_for_Instructors_Module_1-6_Principles_of_Lasers_3rd_Ed PPT: FLL_Figures_and_Images_for_Instructors_Module_1-6_Principles_of_Lasers_3rd_Ed

Course 2: Laser Systems and Applications, 2nd Edition

Course 2, Laser Systems and Applications, 2nd Edition, contains the following ten modules: 1. Laser Q-Switching, Mode Locking, and Frequency Doubling 2. Laser Output Characteristics 3. Laser Types and Their Applications 4. Carbon Dioxide Lasers and Their Applications 5. Fiber Lasers and Their Applications 6. Diode Lasers and Their Applications 7. Argon-Ion Lasers and Their Applications 8. Nd:YAG Lasers and Their Applications 9. Excimer Lasers and Their Applications 10. Systems Integration in Photonics

• Complete indexes, located at the end of each module.
• An “Acronym Glossary,” located at the back of the text.
• Lab videos, showing setup, operation, safety precautions and some measurements.
• Copies of all the figures used in the modules. A PDF and a PowerPoint version are available.
• Student Assignment Videos: A listing of 5-8 minute videos that will further explain the content or demonstrate an application for each of the first 9 modules.
• Student Assignment Questions for use with each video.

Laser Systems:  Operating principles, output characteristics, diagnostics, and applications for the six most   widely used laser types. All important lasers are described and classified according to their active medium, output wavelength, and applications.

Real-World Applications:  Students want to know what skills and knowledge they will need to succeed in future jobs and what kinds of responsibilities they might be assigned in the workplace. This text has three features that address these interests and bring real-world context to its content.

Safety Considerations:  Students must understand that a main consideration of any photonics technician is safety. Technicians working in the photonics industry are constantly exposed to a variety of radiation sources that can pose safety hazards. To eliminate or minimize these hazards, students must learn the safety protocols for these radiation sources and know how to implement them. To facilitate this learning, each module includes a special section called  Safety Considerations . This section provides information on these protocols and explains to students technicians’ responsibilities in implementing them.

Troubleshooting Strategies:  A prime skill that photonics technicians must master is troubleshooting. All students preparing for careers as photonics technicians need to study and practice the methodology of determining the source of failure in a system. The topic of troubleshooting is integrated throughout the course to provide students with basic strategies for determining the sources of failure in malfunctioning photonics systems and identifying common failure modes in various types of lasers. As they study these troubleshooting strategies, students will experience first-hand the work they will do as photonics technicians and will gain a sense of the skills and knowledge that employers will expect them to have.

Workplace Scenarios:  These problem-based activities allow students to work in groups to generate solutions to problems that can arise in today’s photonics organizations. Students take on technician roles as they work together in teams to use the material in each module to develop strategies for completing assigned tasks. These activities also give students an opportunity to enhance their writing skills: many activities require a report written in the form of an e-mail message or memorandum.

Navigation Enhancements:  Features and additions to supplement navigation within the text.

Acronym Glossary:  A comprehensive listing of the acronyms found within  Laser Systems and Applications . Acronyms are listed and defined in alphabetical order. The Acronym Glossary can be found after Module 2-10.

Module Indexes:  Each module contains an alphabetical listing of terms and ideas contained within that module, and the page numbers where they can be found.

Author(s):  University of Central Florida, National Center for Optics and Photonics Education

ISBN:  978-0-9858006-5-9

Year:  2016

Recommended Grade Level:  College – 2nd Year

PPT: LSA_Figures_and_Images_Module_2-1_Laser_Q-Switching_Mode_Locking_Freq_Doubling   PDF: LSA_Figures_and_Images_for_Instructors_Module_2-1_Laser_Q-Switching_Mode_Locking_Freq_Doubling PPT: LSA_Figures_and_Images_for_Instructors_Module_2-2_Laser_Output_Characteristics PDF: LSA_Figures_and_Images_for_Instructors_Module_2-2_Laser_Output_Characteristics PPT: LSA_Figures_and_Images_for_Instructors_Module_2-3_Laser_Types_and_Their_Applications PDF: LSA_Figures_and_Images_for_Instructors_Module_2-3_Laser_Types_and_Their_Applications PPT: LSA_Figures_and_Images_Module_2-4_Carbon_Dioxide_Lasers_and_Their_Applications   PDF: LSA_Figures_and_Images_for_Instructors_Module_2-4_Carbon_Dioxide_Lasers_and_Their_Applications   PPT: LSA_Figures_and_Images_for_Instructors_Module_2-5_Fiber_Lasers_and_Their_Applications PDF: LSA_Figures_and_Images_for_Instructors_Module_2-5_Fiber_Lasers_and_Their_Applications PPT: LSA_Figures_and_Images_for_Instructors_Module_2-6_Diode_Lasers_and_Their_Applications PDF: LSA_Figures_and_Images_for_Instructors_Module_2-6_Diode_Lasers_and_Their_Applications PPT: LSA_Figures_and_Images_for_Instructors_Module_2-7_Argon-Ion_Lasers_and_Their_Applications PDF: LSA_Figures_and_Images_for_Instructors_Module_2-7_Argon-Ion_Lasers_and_Their_Applications PPT: LSA_Figures_and_Images_for_Instructors_Module_2-8_Nd_YAG_Lasers_and_Their_Applications PDF: LSA_Figures_and_Images_for_Instructors_Module_2-8_Nd_YAG_Lasers_and_Their_Applications PPT: LSA_Figures_and_Images_for_Instructors_Module_2-9_Excimer_Lasers_and_Their_Applications PDF: LSA_Figures_and_Images_for_Instructors_Module_2-9_Excimer_Lasers_and_Their_Applications PPT: LSA_Figures_and_Images_for_Instructors_Module_2-10_Systems_Integration_in_Photonics PDF: LSA_Figures_and_Images_for_Instructors_Module_2-10_Systems_Integration_in_Photonics

Enhancements_and_Faculty_Tools_for_Course_2_Laser_Systems_and_Applications_2nd_Edition_2018

Integrated Photonics

Content covered includes:

• Photonics Integrated Circuits Material and Fabrication Technologies
• Silicon Photonics Integrated Circuits and Devices
• III-V and Compound Semiconductor Devices
• Dielectric and Polymer Waveguides and Waveguide Devices
• Integrated Photonics Circuits and Systems

This course is an excellent introduction to integrated photonics, both for students and industry professionals looking to learn more about an expanding technology.

PPT: IP_Figures_and_Images_for_Instructors_Module_1_Photonic_Integrated_Circuits PDF: IP_Figures_and_Images_for_Instructors_Module_1_Photonic_Integrated_Circuits   PPT: IP_Figures_and_Images_for_2_Silicon_Photonic_Integrated_Circuits PDF: IP_Figures_and_Images_for_2_Silicon_Photonic_Integrated_Circuits   PPT: IP_Figures_and_Images_for_Instructors_Module_3_III-V_Semiconductor_Devices PDF: IP_Figures_and_Images_for_Instructors_Module_3_III-V_Semiconductor_Devices PPT: IP_Figures_and_Images_for_Instructors_Module_4_Dielectric_and_Polymer_Waveguides   PDF: IP_Figures_and_Images_for_Instructors_Module_4_Dielectric_and_Polymer_Waveguides   PPT: IP_Figures_and_Images_for_Instructors_Module_5_Integrated_Photonic_Circuits   PDF: IP_Figures_and_Images_for_Instructors_Module_5_Integrated_Photonic_Circuits  

Introduction to Lasers and Optics

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Augmented reality and virtual reality displays: emerging technologies and future perspectives

• Jianghao Xiong 1 ,
• En-Lin Hsiang 1 ,
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• Liquid crystals

With rapid advances in high-speed communication and computation, augmented reality (AR) and virtual reality (VR) are emerging as next-generation display platforms for deeper human-digital interactions. Nonetheless, to simultaneously match the exceptional performance of human vision and keep the near-eye display module compact and lightweight imposes unprecedented challenges on optical engineering. Fortunately, recent progress in holographic optical elements (HOEs) and lithography-enabled devices provide innovative ways to tackle these obstacles in AR and VR that are otherwise difficult with traditional optics. In this review, we begin with introducing the basic structures of AR and VR headsets, and then describing the operation principles of various HOEs and lithography-enabled devices. Their properties are analyzed in detail, including strong selectivity on wavelength and incident angle, and multiplexing ability of volume HOEs, polarization dependency and active switching of liquid crystal HOEs, device fabrication, and properties of micro-LEDs (light-emitting diodes), and large design freedoms of metasurfaces. Afterwards, we discuss how these devices help enhance the AR and VR performance, with detailed description and analysis of some state-of-the-art architectures. Finally, we cast a perspective on potential developments and research directions of these photonic devices for future AR and VR displays.

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Introduction.

Recent advances in high-speed communication and miniature mobile computing platforms have escalated a strong demand for deeper human-digital interactions beyond traditional flat panel displays. Augmented reality (AR) and virtual reality (VR) headsets 1 , 2 are emerging as next-generation interactive displays with the ability to provide vivid three-dimensional (3D) visual experiences. Their useful applications include education, healthcare, engineering, and gaming, just to name a few 3 , 4 , 5 . VR embraces a total immersive experience, while AR promotes the interaction between user, digital contents, and real world, therefore displaying virtual images while remaining see-through capability. In terms of display performance, AR and VR face several common challenges to satisfy demanding human vision requirements, including field of view (FoV), eyebox, angular resolution, dynamic range, and correct depth cue, etc. Another pressing demand, although not directly related to optical performance, is ergonomics. To provide a user-friendly wearing experience, AR and VR should be lightweight and ideally have a compact, glasses-like form factor. The above-mentioned requirements, nonetheless, often entail several tradeoff relations with one another, which makes the design of high-performance AR/VR glasses/headsets particularly challenging.

In the 1990s, AR/VR experienced the first boom, which quickly subsided due to the lack of eligible hardware and digital content 6 . Over the past decade, the concept of immersive displays was revisited and received a new round of excitement. Emerging technologies like holography and lithography have greatly reshaped the AR/VR display systems. In this article, we firstly review the basic requirements of AR/VR displays and their associated challenges. Then, we briefly describe the properties of two emerging technologies: holographic optical elements (HOEs) and lithography-based devices (Fig. 1 ). Next, we separately introduce VR and AR systems because of their different device structures and requirements. For the immersive VR system, the major challenges and how these emerging technologies help mitigate the problems will be discussed. For the see-through AR system, we firstly review the present status of light engines and introduce some architectures for the optical combiners. Performance summaries on microdisplay light engines and optical combiners will be provided, that serve as a comprehensive overview of the current AR display systems.

The left side illustrates HOEs and lithography-based devices. The right side shows the challenges in VR and architectures in AR, and how the emerging technologies can be applied

Key parameters of AR and VR displays

AR and VR displays face several common challenges to satisfy the demanding human vision requirements, such as FoV, eyebox, angular resolution, dynamic range, and correct depth cue, etc. These requirements often exhibit tradeoffs with one another. Before diving into detailed relations, it is beneficial to review the basic definitions of the above-mentioned display parameters.

Definition of parameters

Taking a VR system (Fig. 2a ) as an example. The light emitting from the display module is projected to a FoV, which can be translated to the size of the image perceived by the viewer. For reference, human vision’s horizontal FoV can be as large as 160° for monocular vision and 120° for overlapped binocular vision 6 . The intersection area of ray bundles forms the exit pupil, which is usually correlated with another parameter called eyebox. The eyebox defines the region within which the whole image FoV can be viewed without vignetting. It therefore generally manifests a 3D geometry 7 , whose volume is strongly dependent on the exit pupil size. A larger eyebox offers more tolerance to accommodate the user’s diversified interpupillary distance (IPD) and wiggling of headset when in use. Angular resolution is defined by dividing the total resolution of the display panel by FoV, which measures the sharpness of a perceived image. For reference, a human visual acuity of 20/20 amounts to 1 arcmin angular resolution, or 60 pixels per degree (PPD), which is considered as a common goal for AR and VR displays. Another important feature of a 3D display is depth cue. Depth cue can be induced by displaying two separate images to the left eye and the right eye, which forms the vergence cue. But the fixed depth of the displayed image often mismatches with the actual depth of the intended 3D image, which leads to incorrect accommodation cues. This mismatch causes the so-called vergence-accommodation conflict (VAC), which will be discussed in detail later. One important observation is that the VAC issue may be more serious in AR than VR, because the image in an AR display is directly superimposed onto the real-world with correct depth cues. The image contrast is dependent on the display panel and stray light. To achieve a high dynamic range, the display panel should exhibit high brightness, low dark level, and more than 10-bits of gray levels. Nowadays, the display brightness of a typical VR headset is about 150–200 cd/m 2 (or nits).

a Schematic of a VR display defining FoV, exit pupil, eyebox, angular resolution, and accommodation cue mismatch. b Sketch of an AR display illustrating ACR

Figure 2b depicts a generic structure of an AR display. The definition of above parameters remains the same. One major difference is the influence of ambient light on the image contrast. For a see-through AR display, ambient contrast ratio (ACR) 8 is commonly used to quantify the image contrast:

where L on ( L off ) represents the on (off)-state luminance (unit: nit), L am is the ambient luminance, and T is the see-through transmittance. In general, ambient light is measured in illuminance (lux). For the convenience of comparison, we convert illuminance to luminance by dividing a factor of π, assuming the emission profile is Lambertian. In a normal living room, the illuminance is about 100 lux (i.e., L am  ≈ 30 nits), while in a typical office lighting condition, L am  ≈ 150 nits. For outdoors, on an overcast day, L am  ≈ 300 nits, and L am  ≈ 3000 nits on a sunny day. For AR displays, a minimum ACR should be 3:1 for recognizable images, 5:1 for adequate readability, and ≥10:1 for outstanding readability. To make a simple estimate without considering all the optical losses, to achieve ACR = 10:1 in a sunny day (~3000 nits), the display needs to deliver a brightness of at least 30,000 nits. This imposes big challenges in finding a high brightness microdisplay and designing a low loss optical combiner.

Tradeoffs and potential solutions

Next, let us briefly review the tradeoff relations mentioned earlier. To begin with, a larger FoV leads to a lower angular resolution for a given display resolution. In theory, to overcome this tradeoff only requires a high-resolution-display source, along with high-quality optics to support the corresponding modulation transfer function (MTF). To attain 60 PPD across 100° FoV requires a 6K resolution for each eye. This may be realizable in VR headsets because a large display panel, say 2–3 inches, can still accommodate a high resolution with acceptable manufacture cost. However, for a glasses-like wearable AR display, the conflict between small display size and the high solution becomes obvious as further shrinking the pixel size of a microdisplay is challenging.

To circumvent this issue, the concept of the foveated display is proposed 9 , 10 , 11 , 12 , 13 . The idea is based on that the human eye only has high visual acuity in the central fovea region, which accounts for about 10° FoV. If the high-resolution image is only projected to fovea while the peripheral image remains low resolution, then a microdisplay with 2K resolution can satisfy the need. Regarding the implementation method of foveated display, a straightforward way is to optically combine two display sources 9 , 10 , 11 : one for foveal and one for peripheral FoV. This approach can be regarded as spatial multiplexing of displays. Alternatively, time-multiplexing can also be adopted, by temporally changing the optical path to produce different magnification factors for the corresponding FoV 12 . Finally, another approach without multiplexing is to use a specially designed lens with intended distortion to achieve non-uniform resolution density 13 . Aside from the implementation of foveation, another great challenge is to dynamically steer the foveated region as the viewer’s eye moves. This task is strongly related to pupil steering, which will be discussed in detail later.

A larger eyebox or FoV usually decreases the image brightness, which often lowers the ACR. This is exactly the case for a waveguide AR system with exit pupil expansion (EPE) while operating under a strong ambient light. To improve ACR, one approach is to dynamically adjust the transmittance with a tunable dimmer 14 , 15 . Another solution is to directly boost the image brightness with a high luminance microdisplay and an efficient combiner optics. Details of this topic will be discussed in the light engine section.

Another tradeoff of FoV and eyebox in geometric optical systems results from the conservation of etendue (or optical invariant). To increase the system etendue requires a larger optics, which in turn compromises the form factor. Finally, to address the VAC issue, the display system needs to generate a proper accommodation cue, which often requires the modulation of image depth or wavefront, neither of which can be easily achieved in a traditional geometric optical system. While remarkable progresses have been made to adopt freeform surfaces 16 , 17 , 18 , to further advance AR and VR systems requires additional novel optics with a higher degree of freedom in structure design and light modulation. Moreover, the employed optics should be thin and lightweight. To mitigate the above-mentioned challenges, diffractive optics is a strong contender. Unlike geometric optics relying on curved surfaces to refract or reflect light, diffractive optics only requires a thin layer of several micrometers to establish efficient light diffractions. Two major types of diffractive optics are HOEs based on wavefront recording and manually written devices like surface relief gratings (SRGs) based on lithography. While SRGs have large design freedoms of local grating geometry, a recent publication 19 indicates the combination of HOE and freeform optics can also offer a great potential for arbitrary wavefront generation. Furthermore, the advances in lithography have also enabled optical metasurfaces beyond diffractive and refractive optics, and miniature display panels like micro-LED (light-emitting diode). These devices hold the potential to boost the performance of current AR/VR displays, while keeping a lightweight and compact form factor.

Formation and properties of HOEs

HOE generally refers to a recorded hologram that reproduces the original light wavefront. The concept of holography is proposed by Dennis Gabor 20 , which refers to the process of recording a wavefront in a medium (hologram) and later reconstructing it with a reference beam. Early holography uses intensity-sensitive recording materials like silver halide emulsion, dichromated gelatin, and photopolymer 21 . Among them, photopolymer stands out due to its easy fabrication and ability to capture high-fidelity patterns 22 , 23 . It has therefore found extensive applications like holographic data storage 23 and display 24 , 25 . Photopolymer HOEs (PPHOEs) have a relatively small refractive index modulation and therefore exhibits a strong selectivity on the wavelength and incident angle. Another feature of PPHOE is that several holograms can be recorded into a photopolymer film by consecutive exposures. Later, liquid-crystal holographic optical elements (LCHOEs) based on photoalignment polarization holography have also been developed 25 , 26 . Due to the inherent anisotropic property of liquid crystals, LCHOEs are extremely sensitive to the polarization state of the input light. This feature, combined with the polarization modulation ability of liquid crystal devices, offers a new possibility for dynamic wavefront modulation in display systems.

The formation of PPHOE is illustrated in Fig. 3a . When exposed to an interfering field with high-and-low intensity fringes, monomers tend to move toward bright fringes due to the higher local monomer-consumption rate. As a result, the density and refractive index is slightly larger in bright regions. Note the index modulation δ n here is defined as the difference between the maximum and minimum refractive indices, which may be twice the value in other definitions 27 . The index modulation δ n is typically in the range of 0–0.06. To understand the optical properties of PPHOE, we simulate a transmissive grating and a reflective grating using rigorous coupled-wave analysis (RCWA) 28 , 29 and plot the results in Fig. 3b . Details of grating configuration can be found in Table S1 . Here, the reason for only simulating gratings is that for a general HOE, the local region can be treated as a grating. The observation of gratings can therefore offer a general insight of HOEs. For a transmissive grating, its angular bandwidth (efficiency > 80%) is around 5° ( λ  = 550 nm), while the spectral band is relatively broad, with bandwidth around 175 nm (7° incidence). For a reflective grating, its spectral band is narrow, with bandwidth around 10 nm. The angular bandwidth varies with the wavelength, ranging from 2° to 20°. The strong selectivity of PPHOE on wavelength and incident angle is directly related to its small δ n , which can be adjusted by controlling the exposure dosage.

a Schematic of the formation of PPHOE. Simulated efficiency plots for b1 transmissive and b2 reflective PPHOEs. c Working principle of multiplexed PPHOE. d Formation and molecular configurations of LCHOEs. Simulated efficiency plots for e1 transmissive and e2 reflective LCHOEs. f Illustration of polarization dependency of LCHOEs

A distinctive feature of PPHOE is the ability to multiplex several holograms into one film sample. If the exposure dosage of a recording process is controlled so that the monomers are not completely depleted in the first exposure, the remaining monomers can continue to form another hologram in the following recording process. Because the total amount of monomer is fixed, there is usually an efficiency tradeoff between multiplexed holograms. The final film sample would exhibit the wavefront modulation functions of multiple holograms (Fig. 3c ).

Liquid crystals have also been used to form HOEs. LCHOEs can generally be categorized into volume-recording type and surface-alignment type. Volume-recording type LCHOEs are either based on early polarization holography recordings with azo-polymer 30 , 31 , or holographic polymer-dispersed liquid crystals (HPDLCs) 32 , 33 formed by liquid-crystal-doped photopolymer. Surface-alignment type LCHOEs are based on photoalignment polarization holography (PAPH) 34 . The first step is to record the desired polarization pattern in a thin photoalignment layer, and the second step is to use it to align the bulk liquid crystal 25 , 35 . Due to the simple fabrication process, high efficiency, and low scattering from liquid crystal’s self-assembly nature, surface-alignment type LCHOEs based on PAPH have recently attracted increasing interest in applications like near-eye displays. Here, we shall focus on this type of surface-alignment LCHOE and refer to it as LCHOE thereafter for simplicity.

The formation of LCHOEs is illustrated in Fig. 3d . The information of the wavefront and the local diffraction pattern is recorded in a thin photoalignment layer. The volume liquid crystal deposited on the photoalignment layer, depending on whether it is nematic liquid crystal or cholesteric liquid crystal (CLC), forms a transmissive or a reflective LCHOE. In a transmissive LCHOE, the bulk nematic liquid crystal molecules generally follow the pattern of the bottom alignment layer. The smallest allowable pattern period is governed by the liquid crystal distortion-free energy model, which predicts the pattern period should generally be larger than sample thickness 36 , 37 . This results in a maximum diffraction angle under 20°. On the other hand, in a reflective LCHOE 38 , 39 , the bulk CLC molecules form a stable helical structure, which is tilted to match the k -vector of the bottom pattern. The structure exhibits a very low distorted free energy 40 , 41 and can accommodate a pattern period that is small enough to diffract light into the total internal reflection (TIR) of a glass substrate.

The diffraction property of LCHOEs is shown in Fig. 3e . The maximum refractive index modulation of LCHOE is equal to the liquid crystal birefringence (Δ n ), which may vary from 0.04 to 0.5, depending on the molecular conjugation 42 , 43 . The birefringence used in our simulation is Δ n  = 0.15. Compared to PPHOEs, the angular and spectral bandwidths are significantly larger for both transmissive and reflective LCHOEs. For a transmissive LCHOE, its angular bandwidth is around 20° ( λ  = 550 nm), while the spectral bandwidth is around 300 nm (7° incidence). For a reflective LCHOE, its spectral bandwidth is around 80 nm and angular bandwidth could vary from 15° to 50°, depending on the wavelength.

The anisotropic nature of liquid crystal leads to LCHOE’s unique polarization-dependent response to an incident light. As depicted in Fig. 3f , for a transmissive LCHOE the accumulated phase is opposite for the conjugated left-handed circular polarization (LCP) and right-handed circular polarization (RCP) states, leading to reversed diffraction directions. For a reflective LCHOE, the polarization dependency is similar to that of a normal CLC. For the circular polarization with the same handedness as the helical structure of CLC, the diffraction is strong. For the opposite circular polarization, the diffraction is negligible.

Another distinctive property of liquid crystal is its dynamic response to an external voltage. The LC reorientation can be controlled with a relatively low voltage (<10 V rms ) and the response time is on the order of milliseconds, depending mainly on the LC viscosity and layer thickness. Methods to dynamically control LCHOEs can be categorized as active addressing and passive addressing, which can be achieved by either directly switching the LCHOE or modulating the polarization state with an active waveplate. Detailed addressing methods will be described in the VAC section.

Lithography-enabled devices

Lithography technologies are used to create arbitrary patterns on wafers, which lays the foundation of the modern integrated circuit industry 44 . Photolithography is suitable for mass production while electron/ion beam lithography is usually used to create photomask for photolithography or to write structures with nanometer-scale feature size. Recent advances in lithography have enabled engineered structures like optical metasurfaces 45 , SRGs 46 , as well as micro-LED displays 47 . Metasurfaces exhibit a remarkable design freedom by varying the shape of meta-atoms, which can be utilized to achieve novel functions like achromatic focus 48 and beam steering 49 . Similarly, SRGs also offer a large design freedom by manipulating the geometry of local grating regions to realize desired optical properties. On the other hand, micro-LED exhibits several unique features, such as ultrahigh peak brightness, small aperture ratio, excellent stability, and nanosecond response time, etc. As a result, micro-LED is a promising candidate for AR and VR systems for achieving high ACR and high frame rate for suppressing motion image blurs. In the following section, we will briefly review the fabrication and properties of micro-LEDs and optical modulators like metasurfaces and SRGs.

Fabrication and properties of micro-LEDs

LEDs with a chip size larger than 300 μm have been widely used in solid-state lighting and public information displays. Recently, micro-LEDs with chip sizes <5 μm have been demonstrated 50 . The first micro-LED disc with a diameter of about 12 µm was demonstrated in 2000 51 . After that, a single color (blue or green) LED microdisplay was demonstrated in 2012 52 . The high peak brightness, fast response time, true dark state, and long lifetime of micro-LEDs are attractive for display applications. Therefore, many companies have since released their micro-LED prototypes or products, ranging from large-size TVs to small-size microdisplays for AR/VR applications 53 , 54 . Here, we focus on micro-LEDs for near-eye display applications. Regarding the fabrication of micro-LEDs, through the metal-organic chemical vapor deposition (MOCVD) method, the AlGaInP epitaxial layer is grown on GaAs substrate for red LEDs, and GaN epitaxial layers on sapphire substrate for green and blue LEDs. Next, a photolithography process is applied to define the mesa and deposit electrodes. To drive the LED array, the fabricated micro-LEDs are transferred to a CMOS (complementary metal oxide semiconductor) driver board. For a small size (<2 inches) microdisplay used in AR or VR, the precision of the pick-and-place transfer process is hard to meet the high-resolution-density (>1000 pixel per inch) requirement. Thus, the main approach to assemble LED chips with driving circuits is flip-chip bonding 50 , 55 , 56 , 57 , as Fig. 4a depicts. In flip-chip bonding, the mesa and electrode pads should be defined and deposited before the transfer process, while metal bonding balls should be preprocessed on the CMOS substrate. After that, thermal-compression method is used to bond the two wafers together. However, due to the thermal mismatch of LED chip and driving board, as the pixel size decreases, the misalignment between the LED chip and the metal bonding ball on the CMOS substrate becomes serious. In addition, the common n-GaN layer may cause optical crosstalk between pixels, which degrades the image quality. To overcome these issues, the LED epitaxial layer can be firstly metal-bonded with the silicon driver board, followed by the photolithography process to define the LED mesas and electrodes. Without the need for an alignment process, the pixel size can be reduced to <5 µm 50 .

a Illustration of flip-chip bonding technology. b Simulated IQE-LED size relations for red and blue LEDs based on ABC model. c Comparison of EQE of different LED sizes with and without KOH and ALD side wall treatment. d Angular emission profiles of LEDs with different sizes. Metasurfaces based on e resonance-tuning, f non-resonance tuning and g combination of both. h Replication master and i replicated SRG based on nanoimprint lithography. Reproduced from a ref. 55 with permission from AIP Publishing, b ref. 61 with permission from PNAS, c ref. 66 with permission from IOP Publishing, d ref. 67 with permission from AIP Publishing, e ref. 69 with permission from OSA Publishing f ref. 48 with permission from AAAS g ref. 70 with permission from AAAS and h , i ref. 85 with permission from OSA Publishing

In addition to manufacturing process, the electrical and optical characteristics of LED also depend on the chip size. Generally, due to Shockley-Read-Hall (SRH) non-radiative recombination on the sidewall of active area, a smaller LED chip size results in a lower internal quantum efficiency (IQE), so that the peak IQE driving point will move toward a higher current density due to increased ratio of sidewall surface to active volume 58 , 59 , 60 . In addition, compared to the GaN-based green and blue LEDs, the AlGaInP-based red LEDs with a larger surface recombination and carrier diffusion length suffer a more severe efficiency drop 61 , 62 . Figure 4b shows the simulated result of IQE drop in relation with the LED chip size of blue and red LEDs based on ABC model 63 . To alleviate the efficiency drop caused by sidewall defects, depositing passivation materials by atomic layer deposition (ALD) or plasma enhanced chemical vapor deposition (PECVD) is proven to be helpful for both GaN and AlGaInP based LEDs 64 , 65 . In addition, applying KOH (Potassium hydroxide) treatment after ALD can further reduce the EQE drop of micro-LEDs 66 (Fig. 4c ). Small-size LEDs also exhibit some advantages, such as higher light extraction efficiency (LEE). Compared to an 100-µm LED, the LEE of a 2-µm LED increases from 12.2 to 25.1% 67 . Moreover, the radiation pattern of micro-LED is more directional than that of a large-size LED (Fig. 4d ). This helps to improve the lens collection efficiency in AR/VR display systems.

Metasurfaces and SGs

Thanks to the advances in lithography technology, low-loss dielectric metasurfaces working in the visible band have recently emerged as a platform for wavefront shaping 45 , 48 , 68 . They consist of an array of subwavelength-spaced structures with individually engineered wavelength-dependent polarization/phase/ amplitude response. In general, the light modulation mechanisms can be classified into resonant tuning 69 (Fig. 4e ), non-resonant tuning 48 (Fig. 4f ), and combination of both 70 (Fig. 4g ). In comparison with non-resonant tuning (based on geometric phase and/or dynamic propagation phase), the resonant tuning (such as Fabry–Pérot resonance, Mie resonance, etc.) is usually associated with a narrower operating bandwidth and a smaller out-of-plane aspect ratio (height/width) of nanostructures. As a result, they are easier to fabricate but more sensitive to fabrication tolerances. For both types, materials with a higher refractive index and lower absorption loss are beneficial to reduce the aspect ratio of nanostructure and improve the device efficiency. To this end, titanium dioxide (TiO 2 ) and gallium nitride (GaN) are the major choices for operating in the entire visible band 68 , 71 . While small-sized metasurfaces (diameter <1 mm) are usually fabricated via electron-beam lithography or focused ion beam milling in the labs, the ability of mass production is the key to their practical adoption. The deep ultraviolet (UV) photolithography has proven its feasibility for reproducing centimeter-size metalenses with decent imaging performance, while it requires multiple steps of etching 72 . Interestingly, the recently developed UV nanoimprint lithography based on a high-index nanocomposite only takes a single step and can obtain an aspect ratio larger than 10, which shows great promise for high-volume production 73 .

The arbitrary wavefront shaping capability and the thinness of the metasurfaces have aroused strong research interests in the development of novel AR/VR prototypes with improved performance. Lee et al. employed nanoimprint lithography to fabricate a centimeter-size, geometric-phase metalens eyepiece for full-color AR displays 74 . Through tailoring its polarization conversion efficiency and stacking with a circular polarizer, the virtual image can be superimposed with the surrounding scene. The large numerical aperture (NA~0.5) of the metalens eyepiece enables a wide FoV (>76°) that conventional optics are difficult to obtain. However, the geometric phase metalens is intrinsically a diffractive lens that also suffers from strong chromatic aberrations. To overcome this issue, an achromatic lens can be designed via simultaneously engineering the group delay and the group delay dispersion 75 , 76 , which will be described in detail later. Other novel and/or improved near-eye display architectures include metasurface-based contact lens-type AR 77 , achromatic metalens array enabled integral-imaging light field displays 78 , wide FoV lightguide AR with polarization-dependent metagratings 79 , and off-axis projection-type AR with an aberration-corrected metasurface combiner 80 , 81 , 82 . Nevertheless, from the existing AR/VR prototypes, metasurfaces still face a strong tradeoff between numerical aperture (for metalenses), chromatic aberration, monochromatic aberration, efficiency, aperture size, and fabrication complexity.

On the other hand, SRGs are diffractive gratings that have been researched for decades as input/output couplers of waveguides 83 , 84 . Their surface is composed of corrugated microstructures, and different shapes including binary, blazed, slanted, and even analogue can be designed. The parameters of the corrugated microstructures are determined by the target diffraction order, operation spectral bandwidth, and angular bandwidth. Compared to metasurfaces, SRGs have a much larger feature size and thus can be fabricated via UV photolithography and subsequent etching. They are usually replicated by nanoimprint lithography with appropriate heating and surface treatment. According to a report published a decade ago, SRGs with a height of 300 nm and a slant angle of up to 50° can be faithfully replicated with high yield and reproducibility 85 (Fig. 4g, h ).

Challenges and solutions of VR displays

The fully immersive nature of VR headset leads to a relatively fixed configuration where the display panel is placed in front of the viewer’s eye and an imaging optics is placed in-between. Regarding the system performance, although inadequate angular resolution still exists in some current VR headsets, the improvement of display panel resolution with advanced fabrication process is expected to solve this issue progressively. Therefore, in the following discussion, we will mainly focus on two major challenges: form factor and 3D cue generation.

Form factor

Compact and lightweight near-eye displays are essential for a comfortable user experience and therefore highly desirable in VR headsets. Current mainstream VR headsets usually have a considerably larger volume than eyeglasses, and most of the volume is just empty. This is because a certain distance is required between the display panel and the viewing optics, which is usually close to the focal length of the lens system as illustrated in Fig. 5a . Conventional VR headsets employ a transmissive lens with ~4 cm focal length to offer a large FoV and eyebox. Fresnel lenses are thinner than conventional ones, but the distance required between the lens and the panel does not change significantly. In addition, the diffraction artifacts and stray light caused by the Fresnel grooves can degrade the image quality, or MTF. Although the resolution density, quantified as pixel per inch (PPI), of current VR headsets is still limited, eventually Fresnel lens will not be an ideal solution when a high PPI display is available. The strong chromatic aberration of Fresnel singlet should also be compensated if a high-quality imaging system is preferred.

a Schematic of a basic VR optical configuration. b Achromatic metalens used as VR eyepiece. c VR based on curved display and lenslet array. d Basic working principle of a VR display based on pancake optics. e VR with pancake optics and Fresnel lens array. f VR with pancake optics based on purely HOEs. Reprinted from b ref. 87 under the Creative Commons Attribution 4.0 License. Adapted from c ref. 88 with permission from IEEE, e ref. 91 and f ref. 92 under the Creative Commons Attribution 4.0 License

It is tempting to replace the refractive elements with a single thin diffractive lens like a transmissive LCHOE. However, the diffractive nature of such a lens will result in serious color aberrations. Interestingly, metalenses can fulfil this objective without color issues. To understand how metalenses achieve achromatic focus, let us first take a glance at the general lens phase profile \(\Phi (\omega ,r)\) expanded as a Taylor series 75 :

where \(\varphi _0(\omega )\) is the phase at the lens center, \(F\left( \omega \right)\) is the focal length as a function of frequency ω , r is the radial coordinate, and \(\omega _0\) is the central operation frequency. To realize achromatic focus, \(\partial F{{{\mathrm{/}}}}\partial \omega\) should be zero. With a designed focal length, the group delay \(\partial \Phi (\omega ,r){{{\mathrm{/}}}}\partial \omega\) and the group delay dispersion \(\partial ^2\Phi (\omega ,r){{{\mathrm{/}}}}\partial \omega ^2\) can be determined, and \(\varphi _0(\omega )\) is an auxiliary degree of freedom of the phase profile design. In the design of an achromatic metalens, the group delay is a function of the radial coordinate and monotonically increases with the metalens radius. Many designs have proven that the group delay has a limited variation range 75 , 76 , 78 , 86 . According to Shrestha et al. 86 , there is an inevitable tradeoff between the maximum radius of the metalens, NA, and operation bandwidth. Thus, the reported achromatic metalenses at visible usually have limited lens aperture (e.g., diameter < 250 μm) and NA (e.g., <0.2). Such a tradeoff is undesirable in VR displays, as the eyepiece favors a large clear aperture (inch size) and a reasonably high NA (>0.3) to maintain a wide FoV and a reasonable eye relief 74 .

To overcome this limitation, Li et al. 87 proposed a novel zone lens method. Unlike the traditional phase Fresnel lens where the zones are determined by the phase reset, the new approach divides the zones by the group delay reset. In this way, the lens aperture and NA can be much enlarged, and the group delay limit is bypassed. A notable side effect of this design is the phase discontinuity at zone boundaries that will contribute to higher-order focusing. Therefore, significant efforts have been conducted to find the optimal zone transition locations and to minimize the phase discontinuities. Using this method, they have demonstrated an impressive 2-mm-diameter metalens with NA = 0.7 and nearly diffraction-limited focusing for the designed wavelengths (488, 532, 658 nm) (Fig. 5b ). Such a metalens consists of 681 zones and works for the visible band ranging from 470 to 670 nm, though the focusing efficiency is in the order of 10%. This is a great starting point for the achromatic metalens to be employed as a compact, chromatic-aberration-free eyepiece in near-eye displays. Future challenges are how to further increase the aperture size, correct the off-axis aberrations, and improve the optical efficiency.

Besides replacing the refractive lens with an achromatic metalens, another way to reduce system focal length without decreasing NA is to use a lenslet array 88 . As depicted in Fig. 5c , both the lenslet array and display panel adopt a curved structure. With the latest flexible OLED panel, the display can be easily curved in one dimension. The system exhibits a large diagonal FoV of 180° with an eyebox of 19 by 12 mm. The geometry of each lenslet is optimized separately to achieve an overall performance with high image quality and reduced distortions.

Aside from trying to shorten the system focal length, another way to reduce total track is to fold optical path. Recently, polarization-based folded lenses, also known as pancake optics, are under active development for VR applications 89 , 90 . Figure 5d depicts the structure of an exemplary singlet pancake VR lens system. The pancake lenses can offer better imaging performance with a compact form factor since there are more degrees of freedom in the design and the actual light path is folded thrice. By using a reflective surface with a positive power, the field curvature of positive refractive lenses can be compensated. Also, the reflective surface has no chromatic aberrations and it contributes considerable optical power to the system. Therefore, the optical power of refractive lenses can be smaller, resulting in an even weaker chromatic aberration. Compared to Fresnel lenses, the pancake lenses have smooth surfaces and much fewer diffraction artifacts and stray light. However, such a pancake lens design is not perfect either, whose major shortcoming is low light efficiency. With two incidences of light on the half mirror, the maximum system efficiency is limited to 25% for a polarized input and 12.5% for an unpolarized input light. Moreover, due to the existence of multiple surfaces in the system, stray light caused by surface reflections and polarization leakage may lead to apparent ghost images. As a result, the catadioptric pancake VR headset usually manifests a darker imagery and lower contrast than the corresponding dioptric VR.

Interestingly, the lenslet and pancake optics can be combined to further reduce the system form. Bang et al. 91 demonstrated a compact VR system with a pancake optics and a Fresnel lenslet array. The pancake optics serves to fold the optical path between the display panel and the lenslet array (Fig. 5e ). Another Fresnel lens is used to collect the light from the lenslet array. The system has a decent horizontal FoV of 102° and an eyebox of 8 mm. However, a certain degree of image discontinuity and crosstalk are still present, which can be improved with further optimizations on the Fresnel lens and the lenslet array.

One step further, replacing all conventional optics in catadioptric VR headset with holographic optics can make the whole system even thinner. Maimone and Wang demonstrated such a lightweight, high-resolution, and ultra-compact VR optical system using purely HOEs 92 . This holographic VR optics was made possible by combining several innovative optical components, including a reflective PPHOE, a reflective LCHOE, and a PPHOE-based directional backlight with laser illumination, as shown in Fig. 5f . Since all the optical power is provided by the HOEs with negligible weight and volume, the total physical thickness can be reduced to <10 mm. Also, unlike conventional bulk optics, the optical power of a HOE is independent of its thickness, only subject to the recording process. Another advantage of using holographic optical devices is that they can be engineered to offer distinct phase profiles for different wavelengths and angles of incidence, adding extra degrees of freedom in optical designs for better imaging performance. Although only a single-color backlight has been demonstrated, such a PPHOE has the potential to achieve full-color laser backlight with multiplexing ability. The PPHOE and LCHOE in the pancake optics can also be optimized at different wavelengths for achieving high-quality full-color images.

Vergence-accommodation conflict

Conventional VR displays suffer from VAC, which is a common issue for stereoscopic 3D displays 93 . In current VR display modules, the distance between the display panel and the viewing optics is fixed, which means the VR imagery is displayed at a single depth. However, the image contents are generated by parallax rendering in three dimensions, offering distinct images for two eyes. This approach offers a proper stimulus to vergence but completely ignores the accommodation cue, which leads to the well-known VAC that can cause an uncomfortable user experience. Since the beginning of this century, numerous methods have been proposed to solve this critical issue. Methods to produce accommodation cue include multifocal/varifocal display 94 , holographic display 95 , and integral imaging display 96 . Alternatively, elimination of accommodation cue using a Maxwellian-view display 93 also helps to mitigate the VAC. However, holographic displays and Maxwellian-view displays generally require a totally different optical architecture than current VR systems. They are therefore more suitable for AR displays, which will be discussed later. Integral imaging, on the other hand, has an inherent tradeoff between view number and resolution. For current VR headsets pursuing high resolution to match human visual acuity, it may not be an appealing solution. Therefore, multifocal/varifocal displays that rely on depth modulation is a relatively practical and effective solution for VR headsets. Regarding the working mechanism, multifocal displays present multiple images with different depths to imitate the original 3D scene. Varifocal displays, in contrast, only show one image at each time frame. The image depth matches the viewer’s vergence depth. Nonetheless, the pre-knowledge of the viewer’s vergence depth requires an additional eye-tracking module. Despite different operation principles, a varifocal display can often be converted to a multifocal display as long as the varifocal module has enough modulation bandwidth to support multiple depths in a time frame.

To achieve depth modulation in a VR system, traditional liquid lens 97 , 98 with tunable focus suffers from the small aperture and large aberrations. Alvarez lens 99 is another tunable-focus solution but it requires mechanical adjustment, which adds to system volume and complexity. In comparison, transmissive LCHOEs with polarization dependency can achieve focus adjustment with electronic driving. Its ultra-thinness also satisfies the requirement of small form factors in VR headsets. The diffractive behavior of transmissive LCHOEs is often interpreted by the mechanism of Pancharatnam-Berry phase (also known as geometric phase) 100 . They are therefore often called Pancharatnam-Berry optical elements (PBOEs). The corresponding lens component is referred as Pancharatnam-Berry lens (PBL).

Two main approaches are used to switch the focus of a PBL, active addressing and passive addressing. In active addressing, the PBL itself (made of LC) can be switched by an applied voltage (Fig. 6a ). The optical power of the liquid crystal PBLs can be turned-on and -off by controlling the voltage. Stacking multiple active PBLs can produce 2 N depths, where N is the number of PBLs. The drawback of using active PBLs, however, is the limited spectral bandwidth since their diffraction efficiency is usually optimized at a single wavelength. In passive addressing, the depth modulation is achieved through changing the polarization state of input light by a switchable half-wave plate (HWP) (Fig. 6b ). The focal length can therefore be switched thanks to the polarization sensitivity of PBLs. Although this approach has a slightly more complicated structure, the overall performance can be better than the active one, because the PBLs made of liquid crystal polymer can be designed to manifest high efficiency within the entire visible spectrum 101 , 102 .

Working principles of a depth switching PBL module based on a active addressing and b passive addressing. c A four-depth multifocal display based on time multiplexing. d A two-depth multifocal display based on polarization multiplexing. Reproduced from c ref. 103 with permission from OSA Publishing and d ref. 104 with permission from OSA Publishing

With the PBL module, multifocal displays can be built using time-multiplexing technique. Zhan et al. 103 demonstrated a four-depth multifocal display using two actively switchable liquid crystal PBLs (Fig. 6c ). The display is synchronized with the PBL module, which lowers the frame rate by the number of depths. Alternatively, multifocal displays can also be achieved by polarization-multiplexing, as demonstrated by Tan et al. 104 . The basic principle is to adjust the polarization state of local pixels so the image content on two focal planes of a PBL can be arbitrarily controlled (Fig. 6d ). The advantage of polarization multiplexing is that it does not sacrifice the frame rate, but it can only support two planes because only two orthogonal polarization states are available. Still, it can be combined with time-multiplexing to reduce the frame rate sacrifice by half. Naturally, varifocal displays can also be built with a PBL module. A fast-response 64-depth varifocal module with six PBLs has been demonstrated 105 .

The compact structure of PBL module leads to a natural solution of integrating it with above-mentioned pancake optics. A compact VR headset with dynamic depth modulation to solve VAC is therefore possible in practice. Still, due to the inherent diffractive nature of PBL, the PBL module face the issue of chromatic dispersion of focal length. To compensate for different focal depths for RGB colors may require additional digital corrections in image-rendering.

Architectures of AR displays

Unlike VR displays with a relatively fixed optical configuration, there exist a vast number of architectures in AR displays. Therefore, instead of following the narrative of tackling different challenges, a more appropriate way to review AR displays is to separately introduce each architecture and discuss its associated engineering challenges. An AR display usually consists of a light engine and an optical combiner. The light engine serves as display image source, while the combiner delivers the displayed images to viewer’s eye and in the meantime transmits the environment light. Some performance parameters like frame rate and power consumption are mainly determined by the light engine. Parameters like FoV, eyebox and MTF are primarily dependent on the combiner optics. Moreover, attributes like image brightness, overall efficiency, and form factor are influenced by both light engine and combiner. In this section, we will firstly discuss the light engine, where the latest advances in micro-LED on chip are reviewed and compared with existing microdisplay systems. Then, we will introduce two main types of combiners: free-space combiner and waveguide combiner.

Light engine

The light engine determines several essential properties of the AR system like image brightness, power consumption, frame rate, and basic etendue. Several types of microdisplays have been used in AR, including micro-LED, micro-organic-light-emitting-diodes (micro-OLED), liquid-crystal-on-silicon (LCoS), digital micromirror device (DMD), and laser beam scanning (LBS) based on micro-electromechanical system (MEMS). We will firstly describe the working principles of these devices and then analyze their performance. For those who are more interested in final performance parameters than details, Table 1 provides a comprehensive summary.

Working principles

Micro-LED and micro-OLED are self-emissive display devices. They are usually more compact than LCoS and DMD because no illumination optics is required. The fundamentally different material systems of LED and OLED lead to different approaches to achieve full-color displays. Due to the “green gap” in LEDs, red LEDs are manufactured on a different semiconductor material from green and blue LEDs. Therefore, how to achieve full-color display in high-resolution density microdisplays is quite a challenge for micro-LEDs. Among several solutions under research are two main approaches. The first is to combine three separate red, green and blue (RGB) micro-LED microdisplay panels 106 . Three single-color micro-LED microdisplays are manufactured separately through flip-chip transfer technology. Then, the projected images from three microdisplay panels are integrated by a trichroic prism (Fig. 7a ).

a RGB micro-LED microdisplays combined by a trichroic prism. b QD-based micro-LED microdisplay. c Micro-OLED display with 4032 PPI. Working principles of d LCoS, e DMD, and f MEMS-LBS display modules. Reprinted from a ref. 106 with permission from IEEE, b ref. 108 with permission from Chinese Laser Press, c ref. 121 with permission from Jon Wiley and Sons, d ref. 124 with permission from Spring Nature, e ref. 126 with permission from Springer and f ref. 128 under the Creative Commons Attribution 4.0 License

Another solution is to assemble color-conversion materials like quantum dot (QD) on top of blue or ultraviolet (UV) micro-LEDs 107 , 108 , 109 (Fig. 7b ). The quantum dot color filter (QDCF) on top of the micro-LED array is mainly fabricated by inkjet printing or photolithography 110 , 111 . However, the display performance of color-conversion micro-LED displays is restricted by the low color-conversion efficiency, blue light leakage, and color crosstalk. Extensive efforts have been conducted to improve the QD-micro-LED performance. To boost QD conversion efficiency, structure designs like nanoring 112 and nanohole 113 , 114 have been proposed, which utilize the Förster resonance energy transfer mechanism to transfer excessive excitons in the LED active region to QD. To prevent blue light leakage, methods using color filters or reflectors like distributed Bragg reflector (DBR) 115 and CLC film 116 on top of QDCF are proposed. Compared to color filters that absorb blue light, DBR and CLC film help recycle the leaked blue light to further excite QDs. Other methods to achieve full-color micro-LED display like vertically stacked RGB micro-LED array 61 , 117 , 118 and monolithic wavelength tunable nanowire LED 119 are also under investigation.

Micro-OLED displays can be generally categorized into RGB OLED and white OLED (WOLED). RGB OLED displays have separate sub-pixel structures and optical cavities, which resonate at the desirable wavelength in RGB channels, respectively. To deposit organic materials onto the separated RGB sub-pixels, a fine metal mask (FMM) that defines the deposition area is required. However, high-resolution RGB OLED microdisplays still face challenges due to the shadow effect during the deposition process through FMM. In order to break the limitation, a silicon nitride film with small shadow has been proposed as a mask for high-resolution deposition above 2000 PPI (9.3 µm) 120 .

WOLED displays use color filters to generate color images. Without the process of depositing patterned organic materials, a high-resolution density up to 4000 PPI has been achieved 121 (Fig. 7c ). However, compared to RGB OLED, the color filters in WOLED absorb about 70% of the emitted light, which limits the maximum brightness of the microdisplay. To improve the efficiency and peak brightness of WOLED microdisplays, in 2019 Sony proposed to apply newly designed cathodes (InZnO) and microlens arrays on OLED microdisplays, which increased the peak brightness from 1600 nits to 5000 nits 120 . In addition, OLEDWORKs has proposed a multi-stacked OLED 122 with optimized microcavities whose emission spectra match the transmission bands of the color filters. The multi-stacked OLED shows a higher luminous efficiency (cd/A), but also requires a higher driving voltage. Recently, by using meta-mirrors as bottom reflective anodes, patterned microcavities with more than 10,000 PPI have been obtained 123 . The high-resolution meta-mirrors generate different reflection phases in the RGB sub-pixels to achieve desirable resonant wavelengths. The narrow emission spectra from the microcavity help to reduce the loss from color filters or even eliminate the need of color filters.

LCoS and DMD are light-modulating displays that generate images by controlling the reflection of each pixel. For LCoS, the light modulation is achieved by manipulating the polarization state of output light through independently controlling the liquid crystal reorientation in each pixel 124 , 125 (Fig. 7d ). Both phase-only and amplitude modulators have been employed. DMD is an amplitude modulation device. The modulation is achieved through controlling the tilt angle of bi-stable micromirrors 126 (Fig. 7e ). To generate an image, both LCoS and DMD rely on the light illumination systems, with LED or laser as light source. For LCoS, the generation of color image can be realized either by RGB color filters on LCoS (with white LEDs) or color-sequential addressing (with RGB LEDs or lasers). However, LCoS requires a linearly polarized light source. For an unpolarized LED light source, usually, a polarization recycling system 127 is implemented to improve the optical efficiency. For a single-panel DMD, the color image is mainly obtained through color-sequential addressing. In addition, DMD does not require a polarized light so that it generally exhibits a higher efficiency than LCoS if an unpolarized light source is employed.

MEMS-based LBS 128 , 129 utilizes micromirrors to directly scan RGB laser beams to form two-dimensional (2D) images (Fig. 7f ). Different gray levels are achieved by pulse width modulation (PWM) of the employed laser diodes. In practice, 2D scanning can be achieved either through a 2D scanning mirror or two 1D scanning mirrors with an additional focusing lens after the first mirror. The small size of MEMS mirror offers a very attractive form factor. At the same time, the output image has a large depth-of-focus (DoF), which is ideal for projection displays. One shortcoming, though, is that the small system etendue often hinders its applications in some traditional display systems.

Comparison of light engine performance

There are several important parameters for a light engine, including image resolution, brightness, frame rate, contrast ratio, and form factor. The resolution requirement (>2K) is similar for all types of light engines. The improvement of resolution is usually accomplished through the manufacturing process. Thus, here we shall focus on other three parameters.

Image brightness usually refers to the measured luminance of a light-emitting object. This measurement, however, may not be accurate for a light engine as the light from engine only forms an intermediate image, which is not directly viewed by the user. On the other hand, to solely focus on the brightness of a light engine could be misleading for a wearable display system like AR. Nowadays, data projectors with thousands of lumens are available. But the power consumption is too high for a battery-powered wearable AR display. Therefore, a more appropriate way to evaluate a light engine’s brightness is to use luminous efficacy (lm/W) measured by dividing the final output luminous flux (lm) by the input electric power (W). For a self-emissive device like micro-LED or micro-OLED, the luminous efficacy is directly determined by the device itself. However, for LCoS and DMD, the overall luminous efficacy should take into consideration the light source luminous efficacy, the efficiency of illumination optics, and the efficiency of the employed spatial light modulator (SLM). For a MEMS LBS engine, the efficiency of MEMS mirror can be considered as unity so that the luminous efficacy basically equals to that of the employed laser sources.

As mentioned earlier, each light engine has a different scheme for generating color images. Therefore, we separately list luminous efficacy of each scheme for a more inclusive comparison. For micro-LEDs, the situation is more complicated because the EQE depends on the chip size. Based on previous studies 130 , 131 , 132 , 133 , we separately calculate the luminous efficacy for RGB micro-LEDs with chip size ≈ 20 µm. For the scheme of direct combination of RGB micro-LEDs, the luminous efficacy is around 5 lm/W. For QD-conversion with blue micro-LEDs, the luminous efficacy is around 10 lm/W with the assumption of 100% color conversion efficiency, which has been demonstrated using structure engineering 114 . For micro-OLEDs, the calculated luminous efficacy is about 4–8 lm/W 120 , 122 . However, the lifetime and EQE of blue OLED materials depend on the driving current. To continuously display an image with brightness higher than 10,000 nits may dramatically shorten the device lifetime. The reason we compare the light engine at 10,000 nits is that it is highly desirable to obtain 1000 nits for the displayed image in order to keep ACR>3:1 with a typical AR combiner whose optical efficiency is lower than 10%.

For an LCoS engine using a white LED as light source, the typical optical efficiency of the whole engine is around 10% 127 , 134 . Then the engine luminous efficacy is estimated to be 12 lm/W with a 120 lm/W white LED source. For a color sequential LCoS using RGB LEDs, the absorption loss from color filters is eliminated, but the luminous efficacy of RGB LED source is also decreased to about 30 lm/W due to lower efficiency of red and green LEDs and higher driving current 135 . Therefore, the final luminous efficacy of the color sequential LCoS engine is also around 10 lm/W. If RGB linearly polarized lasers are employed instead of LEDs, then the LCoS engine efficiency can be quite high due to the high degree of collimation. The luminous efficacy of RGB laser source is around 40 lm/W 136 . Therefore, the laser-based LCoS engine is estimated to have a luminous efficacy of 32 lm/W, assuming the engine optical efficiency is 80%. For a DMD engine with RGB LEDs as light source, the optical efficiency is around 50% 137 , 138 , which leads to a luminous efficacy of 15 lm/W. By switching to laser light sources, the situation is similar to LCoS, with the luminous efficacy of about 32 lm/W. Finally, for MEMS-based LBS engine, there is basically no loss from the optics so that the final luminous efficacy is 40 lm/W. Detailed calculations of luminous efficacy can be found in Supplementary Information .

Another aspect of a light engine is the frame rate, which determines the volume of information it can deliver in a unit time. A high volume of information is vital for the construction of a 3D light field to solve the VAC issue. For micro-LEDs, the device response time is around several nanoseconds, which allows for visible light communication with bandwidth up to 1.5 Gbit/s 139 . For an OLED microdisplay, a fast OLED with ~200 MHz bandwidth has been demonstrated 140 . Therefore, the limitation of frame rate is on the driving circuits for both micro-LED and OLED. Another fact concerning driving circuit is the tradeoff between resolution and frame rate as a higher resolution panel means more scanning lines in each frame. So far, an OLED display with 480 Hz frame rate has been demonstrated 141 . For an LCoS, the frame rate is mainly limited by the LC response time. Depending on the LC material used, the response time is around 1 ms for nematic LC or 200 µs for ferroelectric LC (FLC) 125 . Nematic LC allows analog driving, which accommodates gray levels, typically with 8-bit depth. FLC is bistable so that PWM is used to generate gray levels. DMD is also a binary device. The frame rate can reach 30 kHz, which is mainly constrained by the response time of micromirrors. For MEMS-based LBS, the frame rate is limited by the scanning frequency of MEMS mirrors. A frame rate of 60 Hz with around 1 K resolution already requires a resonance frequency of around 50 kHz, with a Q-factor up to 145,000 128 . A higher frame rate or resolution requires a higher Q-factor and larger laser modulation bandwidth, which may be challenging.

Form factor is another crucial aspect for the light engines of near-eye displays. For self-emissive displays, both micro-OLEDs and QD-based micro-LEDs can achieve full color with a single panel. Thus, they are quite compact. A micro-LED display with separate RGB panels naturally have a larger form factor. In applications requiring direct-view full-color panel, the extra combining optics may also increase the volume. It needs to be pointed out, however, that the combing optics may not be necessary for some applications like waveguide displays, because the EPE process results in system’s insensitivity to the spatial positions of input RGB images. Therefore, the form factor of using three RGB micro-LED panels is medium. For LCoS and DMD with RGB LEDs as light source, the form factor would be larger due to the illumination optics. Still, if a lower luminous efficacy can be accepted, then a smaller form factor can be achieved by using a simpler optics 142 . If RGB lasers are used, the collimation optics can be eliminated, which greatly reduces the form factor 143 . For MEMS-LBS, the form factor can be extremely compact due to the tiny size of MEMS mirror and laser module.

Finally, contrast ratio (CR) also plays an important role affecting the observed images 8 . Micro-LEDs and micro-OLEDs are self-emissive so that their CR can be >10 6 :1. For a laser beam scanner, its CR can also achieve 10 6 :1 because the laser can be turned off completely at dark state. On the other hand, LCoS and DMD are reflective displays, and their CR is around 2000:1 to 5000:1 144 , 145 . It is worth pointing out that the CR of a display engine plays a significant role only in the dark ambient. As the ambient brightness increases, the ACR is mainly governed by the display’s peak brightness, as previously discussed.

The performance parameters of different light engines are summarized in Table 1 . Micro-LEDs and micro-OLEDs have similar levels of luminous efficacy. But micro-OLEDs still face the burn-in and lifetime issue when driving at a high current, which hinders its use for a high-brightness image source to some extent. Micro-LEDs are still under active development and the improvement on luminous efficacy from maturing fabrication process could be expected. Both devices have nanosecond response time and can potentially achieve a high frame rate with a well-designed integrated circuit. The frame rate of the driving circuit ultimately determines the motion picture response time 146 . Their self-emissive feature also leads to a small form factor and high contrast ratio. LCoS and DMD engines have similar performance of luminous efficacy, form factor, and contrast ratio. In terms of light modulation, DMD can provide a higher 1-bit frame rate, while LCoS can offer both phase and amplitude modulations. MEMS-based LBS exhibits the highest luminous efficacy so far. It also exhibits an excellent form factor and contrast ratio, but the presently demonstrated 60-Hz frame rate (limited by the MEMS mirrors) could cause image flickering.

Free-space combiners

The term ‘free-space’ generally refers to the case when light is freely propagating in space, as opposed to a waveguide that traps light into TIRs. Regarding the combiner, it can be a partial mirror, as commonly used in AR systems based on traditional geometric optics. Alternatively, the combiner can also be a reflective HOE. The strong chromatic dispersion of HOE necessitates the use of a laser source, which usually leads to a Maxwellian-type system.

Traditional geometric designs

Several systems based on geometric optics are illustrated in Fig. 8 . The simplest design uses a single freeform half-mirror 6 , 147 to directly collimate the displayed images to the viewer’s eye (Fig. 8a ). This design can achieve a large FoV (up to 90°) 147 , but the limited design freedom with a single freeform surface leads to image distortions, also called pupil swim 6 . The placement of half-mirror also results in a relatively bulky form factor. Another design using so-called birdbath optics 6 , 148 is shown in Fig. 8b . Compared to the single-combiner design, birdbath design has an extra optics on the display side, which provides space for aberration correction. The integration of beam splitter provides a folded optical path, which reduces the form factor to some extent. Another way to fold optical path is to use a TIR-prism. Cheng et al. 149 designed a freeform TIR-prism combiner (Fig. 8c ) offering a diagonal FoV of 54° and exit pupil diameter of 8 mm. All the surfaces are freeform, which offer an excellent image quality. To cancel the optical power for the transmitted environmental light, a compensator is added to the TIR prism. The whole system has a well-balanced performance between FoV, eyebox, and form factor. To release the space in front of viewer’s eye, relay optics can be used to form an intermediate image near the combiner 150 , 151 , as illustrated in Fig. 8d . Although the design offers more optical surfaces for aberration correction, the extra lenses also add to system weight and form factor.

a Single freeform surface as the combiner. b Birdbath optics with a beam splitter and a half mirror. c Freeform TIR prism with a compensator. d Relay optics with a half mirror. Adapted from c ref. 149 with permission from OSA Publishing and d ref. 151 with permission from OSA Publishing

Regarding the approaches to solve the VAC issue, the most straightforward way is to integrate a tunable lens into the optical path, like a liquid lens 152 or Alvarez lens 99 , to form a varifocal system. Alternatively, integral imaging 153 , 154 can also be used, by replacing the original display panel with the central depth plane of an integral imaging module. The integral imaging can also be combined with varifocal approach to overcome the tradeoff between resolution and depth of field (DoF) 155 , 156 , 157 . However, the inherent tradeoff between resolution and view number still exists in this case.

Overall, AR displays based on traditional geometric optics have a relatively simple design with a decent FoV (~60°) and eyebox (8 mm) 158 . They also exhibit a reasonable efficiency. To measure the efficiency of an AR combiner, an appropriate measure is to divide the output luminance (unit: nit) by the input luminous flux (unit: lm), which we note as combiner efficiency. For a fixed input luminous flux, the output luminance, or image brightness, is related to the FoV and exit pupil of the combiner system. If we assume no light waste of the combiner system, then the maximum combiner efficiency for a typical diagonal FoV of 60° and exit pupil (10 mm square) is around 17,000 nit/lm (Eq. S2 ). To estimate the combiner efficiency of geometric combiners, we assume 50% of half-mirror transmittance and the efficiency of other optics to be 50%. Then the final combiner efficiency is about 4200 nit/lm, which is a high value in comparison with waveguide combiners. Nonetheless, to further shrink the system size or improve system performance ultimately encounters the etendue conservation issue. In addition, AR systems with traditional geometric optics is hard to achieve a configuration resembling normal flat glasses because the half-mirror has to be tilted to some extent.

Maxwellian-type systems

The Maxwellian view, proposed by James Clerk Maxwell (1860), refers to imaging a point light source in the eye pupil 159 . If the light beam is modulated in the imaging process, a corresponding image can be formed on the retina (Fig. 9a ). Because the point source is much smaller than the eye pupil, the image is always-in-focus on the retina irrespective of the eye lens’ focus. For applications in AR display, the point source is usually a laser with narrow angular and spectral bandwidths. LED light sources can also build a Maxwellian system, by adding an angular filtering module 160 . Regarding the combiner, although in theory a half-mirror can also be used, HOEs are generally preferred because they offer the off-axis configuration that places combiner in a similar position like eyeglasses. In addition, HOEs have a lower reflection of environment light, which provides a more natural appearance of the user behind the display.

a Schematic of the working principle of Maxwellian displays. Maxwellian displays based on b SLM and laser diode light source and c MEMS-LBS with a steering mirror as additional modulation method. Generation of depth cues by d computational digital holography and e scanning of steering mirror to produce multiple views. Adapted from b, d ref. 143 and c, e ref. 167 under the Creative Commons Attribution 4.0 License

To modulate the light, a SLM like LCoS or DMD can be placed in the light path, as shown in Fig. 9b . Alternatively, LBS system can also be used (Fig. 9c ), where the intensity modulation occurs in the laser diode itself. Besides the operation in a normal Maxwellian-view, both implementations offer additional degrees of freedom for light modulation.

For a SLM-based system, there are several options to arrange the SLM pixels 143 , 161 . Maimone et al. 143 demonstrated a Maxwellian AR display with two modes to offer a large-DoF Maxwellian-view, or a holographic view (Fig. 9d ), which is often referred as computer-generated holography (CGH) 162 . To show an always-in-focus image with a large DoF, the image can be directly displayed on an amplitude SLM, or using amplitude encoding for a phase-only SLM 163 . Alternatively, if a 3D scene with correct depth cues is to be presented, then optimization algorithms for CGH can be used to generate a hologram for the SLM. The generated holographic image exhibits the natural focus-and-blur effect like a real 3D object (Fig. 9d ). To better understand this feature, we need to again exploit the concept of etendue. The laser light source can be considered to have a very small etendue due to its excellent collimation. Therefore, the system etendue is provided by the SLM. The micron-sized pixel-pitch of SLM offers a certain maximum diffraction angle, which, multiplied by the SLM size, equals system etendue. By varying the display content on SLM, the final exit pupil size can be changed accordingly. In the case of a large-DoF Maxwellian view, the exit pupil size is small, accompanied by a large FoV. For the holographic display mode, the reduced DoF requires a larger exit pupil with dimension close to the eye pupil. But the FoV is reduced accordingly due to etendue conservation. Another commonly concerned issue with CGH is the computation time. To achieve a real-time CGH rendering flow with an excellent image quality is quite a challenge. Fortunately, with recent advances in algorithm 164 and the introduction of convolutional neural network (CNN) 165 , 166 , this issue is gradually solved with an encouraging pace. Lately, Liang et al. 166 demonstrated a real-time CGH synthesis pipeline with a high image quality. The pipeline comprises an efficient CNN model to generate a complex hologram from a 3D scene and an improved encoding algorithm to convert the complex hologram to a phase-only one. An impressive frame rate of 60 Hz has been achieved on a desktop computing unit.

For LBS-based system, the additional modulation can be achieved by integrating a steering module, as demonstrated by Jang et al. 167 . The steering mirror can shift the focal point (viewpoint) within the eye pupil, therefore effectively expanding the system etendue. When the steering process is fast and the image content is updated simultaneously, correct 3D cues can be generated, as shown in Fig. 9e . However, there exists a tradeoff between the number of viewpoint and the final image frame rate, because the total frames are equally divided into each viewpoint. To boost the frame rate of MEMS-LBS systems by the number of views (e.g., 3 by 3) may be challenging.

Maxwellian-type systems offer several advantages. The system efficiency is usually very high because nearly all the light is delivered into viewer’s eye. The system FoV is determined by the f /# of combiner and a large FoV (~80° in horizontal) can be achieved 143 . The issue of VAC can be mitigated with an infinite-DoF image that deprives accommodation cue, or completely solved by generating a true-3D scene as discussed above. Despite these advantages, one major weakness of Maxwellian-type system is the tiny exit pupil, or eyebox. A small deviation of eye pupil location from the viewpoint results in the complete disappearance of the image. Therefore, to expand eyebox is considered as one of the most important challenges in Maxwellian-type systems.

Pupil duplication and steering

Methods to expand eyebox can be generally categorized into pupil duplication 168 , 169 , 170 , 171 , 172 and pupil steering 9 , 13 , 167 , 173 . Pupil duplication simply generates multiple viewpoints to cover a large area. In contrast, pupil steering dynamically shifts the viewpoint position, depending on the pupil location. Before reviewing detailed implementations of these two methods, it is worth discussing some of their general features. The multiple viewpoints in pupil duplication usually mean to equally divide the total light intensity. In each time frame, however, it is preferable that only one viewpoint enters the user’s eye pupil to avoid ghost image. This requirement, therefore, results in a reduced total light efficiency, while also conditioning the viewpoint separation to be larger than the pupil diameter. In addition, the separation should not be too large to avoid gap between viewpoints. Considering that human pupil diameter changes in response to environment illuminance, the design of viewpoint separation needs special attention. Pupil steering, on the other hand, only produces one viewpoint at each time frame. It is therefore more light-efficient and free from ghost images. But to determine the viewpoint position requires the information of eye pupil location, which demands a real-time eye-tracking module 9 . Another observation is that pupil steering can accommodate multiple viewpoints by its nature. Therefore, a pupil steering system can often be easily converted to a pupil duplication system by simultaneously generating available viewpoints.

To generate multiple viewpoints, one can focus on modulating the incident light or the combiner. Recall that viewpoint is the image of light source. To duplicate or shift light source can achieve pupil duplication or steering accordingly, as illustrated in Fig. 10a . Several schemes of light modulation are depicted in Fig. 10b–e . An array of light sources can be generated with multiple laser diodes (Fig. 10b ). To turn on all or one of the sources achieves pupil duplication or steering. A light source array can also be produced by projecting light on an array-type PPHOE 168 (Fig. 10c ). Apart from direct adjustment of light sources, modulating light on the path can also effectively steer/duplicate the light sources. Using a mechanical steering mirror, the beam can be deflected 167 (Fig. 10d ), which equals to shifting the light source position. Other devices like a grating or beam splitter can also serve as ray deflector/splitter 170 , 171 (Fig. 10e ).

a Schematic of duplicating (or shift) viewpoint by modulation of incident light. Light modulation by b multiple laser diodes, c HOE lens array, d steering mirror and e grating or beam splitters. f Pupil duplication with multiplexed PPHOE. g Pupil steering with LCHOE. Reproduced from c ref. 168 under the Creative Commons Attribution 4.0 License, e ref. 169 with permission from OSA Publishing, f ref. 171 with permission from OSA Publishing and g ref. 173 with permission from OSA Publishing

Nonetheless, one problem of the light source duplication/shifting methods for pupil duplication/steering is that the aberrations in peripheral viewpoints are often serious 168 , 173 . The HOE combiner is usually recorded at one incident angle. For other incident angles with large deviations, considerable aberrations will occur, especially in the scenario of off-axis configuration. To solve this problem, the modulation can be focused on the combiner instead. While the mechanical shifting of combiner 9 can achieve continuous pupil steering, its integration into AR display with a small factor remains a challenge. Alternatively, the versatile functions of HOE offer possible solutions for combiner modulation. Kim and Park 169 demonstrated a pupil duplication system with multiplexed PPHOE (Fig. 10f ). Wavefronts of several viewpoints can be recorded into one PPHOE sample. Three viewpoints with a separation of 3 mm were achieved. However, a slight degree of ghost image and gap can be observed in the viewpoint transition. For a PPHOE to achieve pupil steering, the multiplexed PPHOE needs to record different focal points with different incident angles. If each hologram has no angular crosstalk, then with an additional device to change the light incident angle, the viewpoint can be steered. Alternatively, Xiong et al. 173 demonstrated a pupil steering system with LCHOEs in a simpler configuration (Fig. 10g ). The polarization-sensitive nature of LCHOE enables the controlling of which LCHOE to function with a polarization converter (PC). When the PC is off, the incident RCP light is focused by the right-handed LCHOE. When the PC is turned on, the RCP light is firstly converted to LCP light and passes through the right-handed LCHOE. Then it is focused by the left-handed LCHOE into another viewpoint. To add more viewpoints requires stacking more pairs of PC and LCHOE, which can be achieved in a compact manner with thin glass substrates. In addition, to realize pupil duplication only requires the stacking of multiple low-efficiency LCHOEs. For both PPHOEs and LCHOEs, because the hologram for each viewpoint is recorded independently, the aberrations can be eliminated.

Regarding the system performance, in theory the FoV is not limited and can reach a large value, such as 80° in horizontal direction 143 . The definition of eyebox is different from traditional imaging systems. For a single viewpoint, it has the same size as the eye pupil diameter. But due to the viewpoint steering/duplication capability, the total system eyebox can be expanded accordingly. The combiner efficiency for pupil steering systems can reach 47,000 nit/lm for a FoV of 80° by 80° and pupil diameter of 4 mm (Eq. S2 ). At such a high brightness level, eye safety could be a concern 174 . For a pupil duplication system, the combiner efficiency is decreased by the number of viewpoints. With a 4-by-4 viewpoint array, it can still reach 3000 nit/lm. Despite the potential gain of pupil duplication/steering, when considering the rotation of eyeball, the situation becomes much more complicated 175 . A perfect pupil steering system requires a 5D steering, which proposes a challenge for practical implementation.

Pin-light systems

Recently, another type of display in close relation with Maxwellian view called pin-light display 148 , 176 has been proposed. The general working principle of pin-light display is illustrated in Fig. 11a . Each pin-light source is a Maxwellian view with a large DoF. When the eye pupil is no longer placed near the source point as in Maxwellian view, each image source can only form an elemental view with a small FoV on retina. However, if the image source array is arranged in a proper form, the elemental views can be integrated together to form a large FoV. According to the specific optical architectures, pin-light display can take different forms of implementation. In the initial feasibility demonstration, Maimone et al. 176 used a side-lit waveguide plate as the point light source (Fig. 11b ). The light inside the waveguide plate is extracted by the etched divots, forming a pin-light source array. A transmissive SLM (LCD) is placed behind the waveguide plate to modulate the light intensity and form the image. The display has an impressive FoV of 110° thanks to the large scattering angle range. However, the direct placement of LCD before the eye brings issues of insufficient resolution density and diffraction of background light.

a Schematic drawing of the working principle of pin-light display. b Pin-light display utilizing a pin-light source and a transmissive SLM. c An example of pin-mirror display with a birdbath optics. d SWD system with LBS image source and off-axis lens array. Reprinted from b ref. 176 under the Creative Commons Attribution 4.0 License and d ref. 180 with permission from OSA Publishing

To avoid these issues, architectures using pin-mirrors 177 , 178 , 179 are proposed. In these systems, the final combiner is an array of tiny mirrors 178 , 179 or gratings 177 , in contrast to their counterparts using large-area combiners. An exemplary system with birdbath design is depicted in Fig. 11c . In this case, the pin-mirrors replace the original beam-splitter in the birdbath and can thus shrink the system volume, while at the same time providing large DoF pin-light images. Nonetheless, such a system may still face the etendue conservation issue. Meanwhile, the size of pin-mirror cannot be too small in order to prevent degradation of resolution density due to diffraction. Therefore, its influence on the see-through background should also be considered in the system design.

To overcome the etendue conservation and improve see-through quality, Xiong et al. 180 proposed another type of pin-light system exploiting the etendue expansion property of waveguide, which is also referred as scanning waveguide display (SWD). As illustrated in Fig. 11d , the system uses an LBS as the image source. The collimated scanned laser rays are trapped in the waveguide and encounter an array of off-axis lenses. Upon each encounter, the lens out-couples the laser rays and forms a pin-light source. SWD has the merits of good see-through quality and large etendue. A large FoV of 100° was demonstrated with the help of an ultra-low f /# lens array based on LCHOE. However, some issues like insufficient image resolution density and image non-uniformity remain to be overcome. To further improve the system may require optimization of Gaussian beam profile and additional EPE module 180 .

Overall, pin-light systems inherit the large DoF from Maxwellian view. With adequate number of pin-light sources, the FoV and eyebox can be expanded accordingly. Nonetheless, despite different forms of implementation, a common issue of pin-light system is the image uniformity. The overlapped region of elemental views has a higher light intensity than the non-overlapped region, which becomes even more complicated considering the dynamic change of pupil size. In theory, the displayed image can be pre-processed to compensate for the optical non-uniformity. But that would require knowledge of precise pupil location (and possibly size) and therefore an accurate eye-tracking module 176 . Regarding the system performance, pin-mirror systems modified from other free-space systems generally shares similar FoV and eyebox with original systems. The combiner efficiency may be lower due to the small size of pin-mirrors. SWD, on the other hand, shares the large FoV and DoF with Maxwellian view, and large eyebox with waveguide combiners. The combiner efficiency may also be lower due to the EPE process.

Waveguide combiner

Besides free-space combiners, another common architecture in AR displays is waveguide combiner. The term ‘waveguide’ indicates the light is trapped in a substrate by the TIR process. One distinctive feature of a waveguide combiner is the EPE process that effectively enlarges the system etendue. In the EPE process, a portion of the trapped light is repeatedly coupled out of the waveguide in each TIR. The effective eyebox is therefore enlarged. According to the features of couplers, we divide the waveguide combiners into two types: diffractive and achromatic, as described in the followings.

Diffractive waveguides

As the name implies, diffractive-type waveguides use diffractive elements as couplers. The in-coupler is usually a diffractive grating and the out-coupler in most cases is also a grating with the same period as the in-coupler, but it can also be an off-axis lens with a small curvature to generate image with finite depth. Three major diffractive couplers have been developed: SRGs, photopolymer gratings (PPGs), and liquid crystal gratings (grating-type LCHOE; also known as polarization volume gratings (PVGs)). Some general protocols for coupler design are that the in-coupler should have a relatively high efficiency and the out-coupler should have a uniform light output. A uniform light output usually requires a low-efficiency coupler, with extra degrees of freedom for local modulation of coupling efficiency. Both in-coupler and out-coupler should have an adequate angular bandwidth to accommodate a reasonable FoV. In addition, the out-coupler should also be optimized to avoid undesired diffractions, including the outward diffraction of TIR light and diffraction of environment light into user’s eyes, which are referred as light leakage and rainbow. Suppression of these unwanted diffractions should also be considered in the optimization process of waveguide design, along with performance parameters like efficiency and uniformity.

The basic working principles of diffractive waveguide-based AR systems are illustrated in Fig. 12 . For the SRG-based waveguides 6 , 8 (Fig. 12a ), the in-coupler can be a transmissive-type or a reflective-type 181 , 182 . The grating geometry can be optimized for coupling efficiency with a large degree of freedom 183 . For the out-coupler, a reflective SRG with a large slant angle to suppress the transmission orders is preferred 184 . In addition, a uniform light output usually requires a gradient efficiency distribution in order to compensate for the decreased light intensity in the out-coupling process. This can be achieved by varying the local grating configurations like height and duty cycle 6 . For the PPG-based waveguides 185 (Fig. 12b ), the small angular bandwidth of a high-efficiency transmissive PPG prohibits its use as in-coupler. Therefore, both in-coupler and out-coupler are usually reflective types. The gradient efficiency can be achieved by space-variant exposure to control the local index modulation 186 or local Bragg slant angle variation through freeform exposure 19 . Due to the relatively small angular bandwidth of PPG, to achieve a decent FoV usually requires stacking two 187 or three 188 PPGs together for a single color. The PVG-based waveguides 189 (Fig. 12c ) also prefer reflective PVGs as in-couplers because the transmissive PVGs are much more difficult to fabricate due to the LC alignment issue. In addition, the angular bandwidth of transmissive PVGs in Bragg regime is also not large enough to support a decent FoV 29 . For the out-coupler, the angular bandwidth of a single reflective PVG can usually support a reasonable FoV. To obtain a uniform light output, a polarization management layer 190 consisting of a LC layer with spatially variant orientations can be utilized. It offers an additional degree of freedom to control the polarization state of the TIR light. The diffraction efficiency can therefore be locally controlled due to the strong polarization sensitivity of PVG.

Schematics of waveguide combiners based on a SRGs, b PPGs and c PVGs. Reprinted from a ref. 85 with permission from OSA Publishing, b ref. 185 with permission from John Wiley and Sons and c ref. 189 with permission from OSA Publishing

The above discussion describes the basic working principle of 1D EPE. Nonetheless, for the 1D EPE to produce a large eyebox, the exit pupil in the unexpanded direction of the original image should be large. This proposes design challenges in light engines. Therefore, a 2D EPE is favored for practical applications. To extend EPE in two dimensions, two consecutive 1D EPEs can be used 191 , as depicted in Fig. 13a . The first 1D EPE occurs in the turning grating, where the light is duplicated in y direction and then turned into x direction. Then the light rays encounter the out-coupler and are expanded in x direction. To better understand the 2D EPE process, the k -vector diagram (Fig. 13b ) can be used. For the light propagating in air with wavenumber k 0 , its possible k -values in x and y directions ( k x and k y ) fall within the circle with radius k 0 . When the light is trapped into TIR, k x and k y are outside the circle with radius k 0 and inside the circle with radius nk 0 , where n is the refractive index of the substrate. k x and k y stay unchanged in the TIR process and are only changed in each diffraction process. The central red box in Fig. 13b indicates the possible k values within the system FoV. After the in-coupler, the k values are added by the grating k -vector, shifting the k values into TIR region. The turning grating then applies another k -vector and shifts the k values to near x -axis. Finally, the k values are shifted by the out-coupler and return to the free propagation region in air. One observation is that the size of red box is mostly limited by the width of TIR band. To accommodate a larger FoV, the outer boundary of TIR band needs to be expanded, which amounts to increasing waveguide refractive index. Another important fact is that when k x and k y are near the outer boundary, the uniformity of output light becomes worse. This is because the light propagation angle is near 90° in the waveguide. The spatial distance between two consecutive TIRs becomes so large that the out-coupled beams are spatially separated to an unacceptable degree. The range of possible k values for practical applications is therefore further shrunk due to this fact.

a Schematic of 2D EPE based on two consecutive 1D EPEs. Gray/black arrows indicate light in air/TIR. Black dots denote TIRs. b k-diagram of the two-1D-EPE scheme. c Schematic of 2D EPE with a 2D hexagonal grating d k-diagram of the 2D-grating scheme

Aside from two consecutive 1D EPEs, the 2D EPE can also be directly implemented with a 2D grating 192 . An example using a hexagonal grating is depicted in Fig. 13c . The hexagonal grating can provide k -vectors in six directions. In the k -diagram (Fig. 13d ), after the in-coupling, the k values are distributed into six regions due to multiple diffractions. The out-coupling occurs simultaneously with pupil expansion. Besides a concise out-coupler configuration, the 2D EPE scheme offers more degrees of design freedom than two 1D EPEs because the local grating parameters can be adjusted in a 2D manner. The higher design freedom has the potential to reach a better output light uniformity, but at the cost of a higher computation demand for optimization. Furthermore, the unslanted grating geometry usually leads to a large light leakage and possibly low efficiency. Adding slant to the geometry helps alleviate the issue, but the associated fabrication may be more challenging.

Finally, we discuss the generation of full-color images. One important issue to clarify is that although diffractive gratings are used here, the final image generally has no color dispersion even if we use a broadband light source like LED. This can be easily understood in the 1D EPE scheme. The in-coupler and out-coupler have opposite k -vectors, which cancels the color dispersion for each other. In the 2D EPE schemes, the k -vectors always form a closed loop from in-coupled light to out-coupled light, thus, the color dispersion also vanishes likewise. The issue of using a single waveguide for full-color images actually exists in the consideration of FoV and light uniformity. The breakup of propagation angles for different colors results in varied out-coupling situations for each color. To be more specific, if the red and the blue channels use the same in-coupler, the propagating angle for the red light is larger than that of the blue light. The red light in peripheral FoV is therefore easier to face the mentioned large-angle non-uniformity issue. To acquire a decent FoV and light uniformity, usually two or three layers of waveguides with different grating pitches are adopted.

Regarding the system performance, the eyebox is generally large enough (~10 mm) to accommodate different user’s IPD and alignment shift during operation. A parameter of significant concern for a waveguide combiner is its FoV. From the k -vector analysis, we can conclude the theoretical upper limit is determined by the waveguide refractive index. But the light/color uniformity also influences the effective FoV, over which the degradation of image quality becomes unacceptable. Current diffractive waveguide combiners generally achieve a FoV of about 50°. To further increase FoV, a straightforward method is to use a higher refractive index waveguide. Another is to tile FoV through direct stacking of multiple waveguides or using polarization-sensitive couplers 79 , 193 . As to the optical efficiency, a typical value for the diffractive waveguide combiner is around 50–200 nit/lm 6 , 189 . In addition, waveguide combiners adopting grating out-couplers generate an image with fixed depth at infinity. This leads to the VAC issue. To tackle VAC in waveguide architectures, the most practical way is to generate multiple depths and use the varifocal or multifocal driving scheme, similar to those mentioned in the VR systems. But to add more depths usually means to stack multiple layers of waveguides together 194 . Considering the additional waveguide layers for RGB colors, the final waveguide thickness would undoubtedly increase.

Other parameters special to waveguide includes light leakage, see-through ghost, and rainbow. Light leakage refers to out-coupled light that goes outwards to the environment, as depicted in Fig. 14a . Aside from decreased efficiency, the leakage also brings drawback of unnatural “bright-eye” appearance of the user and privacy issue. Optimization of the grating structure like geometry of SRG may reduce the leakage. See-through ghost is formed by consecutive in-coupling and out-couplings caused by the out-coupler grating, as sketched in Fig. 14b , After the process, a real object with finite depth may produce a ghost image with shift in both FoV and depth. Generally, an out-coupler with higher efficiency suffers more see-through ghost. Rainbow is caused by the diffraction of environment light into user’s eye, as sketched in Fig. 14c . The color dispersion in this case will occur because there is no cancellation of k -vector. Using the k -diagram, we can obtain a deeper insight into the formation of rainbow. Here, we take the EPE structure in Fig. 13a as an example. As depicted in Fig. 14d , after diffractions by the turning grating and the out-coupler grating, the k values are distributed in two circles that shift from the origin by the grating k -vectors. Some diffracted light can enter the see-through FoV and form rainbow. To reduce rainbow, a straightforward way is to use a higher index substrate. With a higher refractive index, the outer boundary of k diagram is expanded, which can accommodate larger grating k -vectors. The enlarged k -vectors would therefore “push” these two circles outwards, leading to a decreased overlapping region with the see-through FoV. Alternatively, an optimized grating structure would also help reduce the rainbow effect by suppressing the unwanted diffraction.

Sketches of formations of a light leakage, b see-through ghost and c rainbow. d Analysis of rainbow formation with k-diagram

Achromatic waveguide

Achromatic waveguide combiners use achromatic elements as couplers. It has the advantage of realizing full-color image with a single waveguide. A typical example of achromatic element is a mirror. The waveguide with partial mirrors as out-coupler is often referred as geometric waveguide 6 , 195 , as depicted in Fig. 15a . The in-coupler in this case is usually a prism to avoid unnecessary color dispersion if using diffractive elements otherwise. The mirrors couple out TIR light consecutively to produce a large eyebox, similarly in a diffractive waveguide. Thanks to the excellent optical property of mirrors, the geometric waveguide usually exhibits a superior image regarding MTF and color uniformity to its diffractive counterparts. Still, the spatially discontinuous configuration of mirrors also results in gaps in eyebox, which may be alleviated by using a dual-layer structure 196 . Wang et al. designed a geometric waveguide display with five partial mirrors (Fig. 15b ). It exhibits a remarkable FoV of 50° by 30° (Fig. 15c ) and an exit pupil of 4 mm with a 1D EPE. To achieve 2D EPE, similar architectures in Fig. 13a can be used by integrating a turning mirror array as the first 1D EPE module 197 . Unfortunately, the k -vector diagrams in Fig. 13b, d cannot be used here because the k values in x-y plane no longer conserve in the in-coupling and out-coupling processes. But some general conclusions remain valid, like a higher refractive index leading to a larger FoV and gradient out-coupling efficiency improving light uniformity.

a Schematic of the system configuration. b Geometric waveguide with five partial mirrors. c Image photos demonstrating system FoV. Adapted from b , c ref. 195 with permission from OSA Publishing

The fabrication process of geometric waveguide involves coating mirrors on cut-apart pieces and integrating them back together, which may result in a high cost, especially for the 2D EPE architecture. Another way to implement an achromatic coupler is to use multiplexed PPHOE 198 , 199 to mimic the behavior of a tilted mirror (Fig. 16a ). To understand the working principle, we can use the diagram in Fig. 16b . The law of reflection states the angle of reflection equals to the angle of incidence. If we translate this behavior to k -vector language, it means the mirror can apply any length of k -vector along its surface normal direction. The k -vector length of the reflected light is always equal to that of the incident light. This puts a condition that the k -vector triangle is isosceles. With a simple geometric deduction, it can be easily observed this leads to the law of reflection. The behavior of a general grating, however, is very different. For simplicity we only consider the main diffraction order. The grating can only apply a k -vector with fixed k x due to the basic diffraction law. For the light with a different incident angle, it needs to apply different k z to produce a diffracted light with equal k -vector length as the incident light. For a grating with a broad angular bandwidth like SRG, the range of k z is wide, forming a lengthy vertical line in Fig. 16b . For a PPG with a narrow angular bandwidth, the line is short and resembles a dot. If multiple of these tiny dots are distributed along the oblique line corresponding to a mirror, then the final multiplexed PPGs can imitate the behavior of a tilted mirror. Such a PPHOE is sometimes referred as a skew-mirror 198 . In theory, to better imitate the mirror, a lot of multiplexed PPGs is preferred, while each PPG has a small index modulation δn . But this proposes a bigger challenge in device fabrication. Recently, Utsugi et al. demonstrated an impressive skew-mirror waveguide based on 54 multiplexed PPGs (Fig. 16c, d ). The display exhibits an effective FoV of 35° by 36°. In the peripheral FoV, there still exists some non-uniformity (Fig. 16e ) due to the out-coupling gap, which is an inherent feature of the flat-type out-couplers.

a System configuration. b Diagram demonstrating how multiplexed PPGs resemble the behavior of a mirror. Photos showing c the system and d image. e Picture demonstrating effective system FoV. Adapted from c – e ref. 199 with permission from ITE

Finally, it is worth mentioning that metasurfaces are also promising to deliver achromatic gratings 200 , 201 for waveguide couplers ascribed to their versatile wavefront shaping capability. The mechanism of the achromatic gratings is similar to that of the achromatic lenses as previously discussed. However, the current development of achromatic metagratings is still in its infancy. Much effort is needed to improve the optical efficiency for in-coupling, control the higher diffraction orders for eliminating ghost images, and enable a large size design for EPE.

Generally, achromatic waveguide combiners exhibit a comparable FoV and eyebox with diffractive combiners, but with a higher efficiency. For a partial-mirror combiner, its combiner efficiency is around 650 nit/lm 197 (2D EPE). For a skew-mirror combiner, although the efficiency of multiplexed PPHOE is relatively low (~1.5%) 199 , the final combiner efficiency of the 1D EPE system is still high (>3000 nit/lm) due to multiple out-couplings.

Table 2 summarizes the performance of different AR combiners. When combing the luminous efficacy in Table 1 and the combiner efficiency in Table 2 , we can have a comprehensive estimate of the total luminance efficiency (nit/W) for different types of systems. Generally, Maxwellian-type combiners with pupil steering have the highest luminance efficiency when partnered with laser-based light engines like laser-backlit LCoS/DMD or MEM-LBS. Geometric optical combiners have well-balanced image performances, but to further shrink the system size remains a challenge. Diffractive waveguides have a relatively low combiner efficiency, which can be remedied by an efficient light engine like MEMS-LBS. Further development of coupler and EPE scheme would also improve the system efficiency and FoV. Achromatic waveguides have a decent combiner efficiency. The single-layer design also enables a smaller form factor. With advances in fabrication process, it may become a strong contender to presently widely used diffractive waveguides.

Conclusions and perspectives

VR and AR are endowed with a high expectation to revolutionize the way we interact with digital world. Accompanied with the expectation are the engineering challenges to squeeze a high-performance display system into a tightly packed module for daily wearing. Although the etendue conservation constitutes a great obstacle on the path, remarkable progresses with innovative optics and photonics continue to take place. Ultra-thin optical elements like PPHOEs and LCHOEs provide alternative solutions to traditional optics. Their unique features of multiplexing capability and polarization dependency further expand the possibility of novel wavefront modulations. At the same time, nanoscale-engineered metasurfaces/SRGs provide large design freedoms to achieve novel functions beyond conventional geometric optical devices. Newly emerged micro-LEDs open an opportunity for compact microdisplays with high peak brightness and good stability. Further advances on device engineering and manufacturing process are expected to boost the performance of metasurfaces/SRGs and micro-LEDs for AR and VR applications.

Data availability

All data needed to evaluate the conclusions in the paper are present in the paper. Additional data related to this paper may be requested from the authors.

Cakmakci, O. & Rolland, J. Head-worn displays: a review. J. Disp. Technol. 2 , 199–216 (2006).

Article   ADS   Google Scholar  

Zhan, T. et al. Augmented reality and virtual reality displays: perspectives and challenges. iScience 23 , 101397 (2020).

Rendon, A. A. et al. The effect of virtual reality gaming on dynamic balance in older adults. Age Ageing 41 , 549–552 (2012).

Article   Google Scholar  

Choi, S., Jung, K. & Noh, S. D. Virtual reality applications in manufacturing industries: past research, present findings, and future directions. Concurrent Eng. 23 , 40–63 (2015).

Li, X. et al. A critical review of virtual and augmented reality (VR/AR) applications in construction safety. Autom. Constr. 86 , 150–162 (2018).

Kress, B. C. Optical Architectures for Augmented-, Virtual-, and Mixed-Reality Headsets (Bellingham: SPIE Press, 2020).

Cholewiak, S. A. et al. A perceptual eyebox for near-eye displays. Opt. Express 28 , 38008–38028 (2020).

Lee, Y. H., Zhan, T. & Wu, S. T. Prospects and challenges in augmented reality displays. Virtual Real. Intell. Hardw. 1 , 10–20 (2019).

Kim, J. et al. Foveated AR: dynamically-foveated augmented reality display. ACM Trans. Graph. 38 , 99 (2019).

Tan, G. J. et al. Foveated imaging for near-eye displays. Opt. Express 26 , 25076–25085 (2018).

Lee, S. et al. Foveated near-eye display for mixed reality using liquid crystal photonics. Sci. Rep. 10 , 16127 (2020).

Yoo, C. et al. Foveated display system based on a doublet geometric phase lens. Opt. Express 28 , 23690–23702 (2020).

Akşit, K. et al. Manufacturing application-driven foveated near-eye displays. IEEE Trans. Vis. Computer Graph. 25 , 1928–1939 (2019).

Zhu, R. D. et al. High-ambient-contrast augmented reality with a tunable transmittance liquid crystal film and a functional reflective polarizer. J. Soc. Inf. Disp. 24 , 229–233 (2016).

Lincoln, P. et al. Scene-adaptive high dynamic range display for low latency augmented reality. In Proc. 21st ACM SIGGRAPH Symposium on Interactive 3D Graphics and Games . (ACM, San Francisco, CA, 2017).

Duerr, F. & Thienpont, H. Freeform imaging systems: fermat’s principle unlocks “first time right” design. Light.: Sci. Appl. 10 , 95 (2021).

Bauer, A., Schiesser, E. M. & Rolland, J. P. Starting geometry creation and design method for freeform optics. Nat. Commun. 9 , 1756 (2018).

Rolland, J. P. et al. Freeform optics for imaging. Optica 8 , 161–176 (2021).

Jang, C. et al. Design and fabrication of freeform holographic optical elements. ACM Trans. Graph. 39 , 184 (2020).

Gabor, D. A new microscopic principle. Nature 161 , 777–778 (1948).

Kostuk, R. K. Holography: Principles and Applications (Boca Raton: CRC Press, 2019).

Lawrence, J. R., O'Neill, F. T. & Sheridan, J. T. Photopolymer holographic recording material. Optik 112 , 449–463 (2001).

Guo, J. X., Gleeson, M. R. & Sheridan, J. T. A review of the optimisation of photopolymer materials for holographic data storage. Phys. Res. Int. 2012 , 803439 (2012).

Jang, C. et al. Recent progress in see-through three-dimensional displays using holographic optical elements [Invited]. Appl. Opt. 55 , A71–A85 (2016).

Xiong, J. H. et al. Holographic optical elements for augmented reality: principles, present status, and future perspectives. Adv. Photonics Res. 2 , 2000049 (2021).

Tabiryan, N. V. et al. Advances in transparent planar optics: enabling large aperture, ultrathin lenses. Adv. Optical Mater. 9 , 2001692 (2021).

Zanutta, A. et al. Photopolymeric films with highly tunable refractive index modulation for high precision diffractive optics. Optical Mater. Express 6 , 252–263 (2016).

Moharam, M. G. & Gaylord, T. K. Rigorous coupled-wave analysis of planar-grating diffraction. J. Optical Soc. Am. 71 , 811–818 (1981).

Xiong, J. H. & Wu, S. T. Rigorous coupled-wave analysis of liquid crystal polarization gratings. Opt. Express 28 , 35960–35971 (2020).

Xie, S., Natansohn, A. & Rochon, P. Recent developments in aromatic azo polymers research. Chem. Mater. 5 , 403–411 (1993).

Shishido, A. Rewritable holograms based on azobenzene-containing liquid-crystalline polymers. Polym. J. 42 , 525–533 (2010).

Bunning, T. J. et al. Holographic polymer-dispersed liquid crystals (H-PDLCs). Annu. Rev. Mater. Sci. 30 , 83–115 (2000).

Liu, Y. J. & Sun, X. W. Holographic polymer-dispersed liquid crystals: materials, formation, and applications. Adv. Optoelectron. 2008 , 684349 (2008).

Xiong, J. H. & Wu, S. T. Planar liquid crystal polarization optics for augmented reality and virtual reality: from fundamentals to applications. eLight 1 , 3 (2021).

Yaroshchuk, O. & Reznikov, Y. Photoalignment of liquid crystals: basics and current trends. J. Mater. Chem. 22 , 286–300 (2012).

Sarkissian, H. et al. Periodically aligned liquid crystal: potential application for projection displays. Mol. Cryst. Liq. Cryst. 451 , 1–19 (2006).

Komanduri, R. K. & Escuti, M. J. Elastic continuum analysis of the liquid crystal polarization grating. Phys. Rev. E 76 , 021701 (2007).

Kobashi, J., Yoshida, H. & Ozaki, M. Planar optics with patterned chiral liquid crystals. Nat. Photonics 10 , 389–392 (2016).

Lee, Y. H., Yin, K. & Wu, S. T. Reflective polarization volume gratings for high efficiency waveguide-coupling augmented reality displays. Opt. Express 25 , 27008–27014 (2017).

Lee, Y. H., He, Z. Q. & Wu, S. T. Optical properties of reflective liquid crystal polarization volume gratings. J. Optical Soc. Am. B 36 , D9–D12 (2019).

Xiong, J. H., Chen, R. & Wu, S. T. Device simulation of liquid crystal polarization gratings. Opt. Express 27 , 18102–18112 (2019).

Czapla, A. et al. Long-period fiber gratings with low-birefringence liquid crystal. Mol. Cryst. Liq. Cryst. 502 , 65–76 (2009).

Dąbrowski, R., Kula, P. & Herman, J. High birefringence liquid crystals. Crystals 3 , 443–482 (2013).

Mack, C. Fundamental Principles of Optical Lithography: The Science of Microfabrication (Chichester: John Wiley & Sons, 2007).

Genevet, P. et al. Recent advances in planar optics: from plasmonic to dielectric metasurfaces. Optica 4 , 139–152 (2017).

Guo, L. J. Nanoimprint lithography: methods and material requirements. Adv. Mater. 19 , 495–513 (2007).

Park, J. et al. Electrically driven mid-submicrometre pixelation of InGaN micro-light-emitting diode displays for augmented-reality glasses. Nat. Photonics 15 , 449–455 (2021).

Khorasaninejad, M. et al. Metalenses at visible wavelengths: diffraction-limited focusing and subwavelength resolution imaging. Science 352 , 1190–1194 (2016).

Li, S. Q. et al. Phase-only transmissive spatial light modulator based on tunable dielectric metasurface. Science 364 , 1087–1090 (2019).

Liang, K. L. et al. Advances in color-converted micro-LED arrays. Jpn. J. Appl. Phys. 60 , SA0802 (2020).

Jin, S. X. et al. GaN microdisk light emitting diodes. Appl. Phys. Lett. 76 , 631–633 (2000).

Day, J. et al. Full-scale self-emissive blue and green microdisplays based on GaN micro-LED arrays. In Proc. SPIE 8268, Quantum Sensing and Nanophotonic Devices IX (SPIE, San Francisco, California, United States, 2012).

Huang, Y. G. et al. Mini-LED, micro-LED and OLED displays: present status and future perspectives. Light.: Sci. Appl. 9 , 105 (2020).

Parbrook, P. J. et al. Micro-light emitting diode: from chips to applications. Laser Photonics Rev. 15 , 2000133 (2021).

Day, J. et al. III-Nitride full-scale high-resolution microdisplays. Appl. Phys. Lett. 99 , 031116 (2011).

Liu, Z. J. et al. 360 PPI flip-chip mounted active matrix addressable light emitting diode on silicon (LEDoS) micro-displays. J. Disp. Technol. 9 , 678–682 (2013).

Zhang, L. et al. Wafer-scale monolithic hybrid integration of Si-based IC and III–V epi-layers—A mass manufacturable approach for active matrix micro-LED micro-displays. J. Soc. Inf. Disp. 26 , 137–145 (2018).

Tian, P. F. et al. Size-dependent efficiency and efficiency droop of blue InGaN micro-light emitting diodes. Appl. Phys. Lett. 101 , 231110 (2012).

Olivier, F. et al. Shockley-Read-Hall and Auger non-radiative recombination in GaN based LEDs: a size effect study. Appl. Phys. Lett. 111 , 022104 (2017).

Konoplev, S. S., Bulashevich, K. A. & Karpov, S. Y. From large-size to micro-LEDs: scaling trends revealed by modeling. Phys. Status Solidi (A) 215 , 1700508 (2018).

Li, L. Z. et al. Transfer-printed, tandem microscale light-emitting diodes for full-color displays. Proc. Natl Acad. Sci. USA 118 , e2023436118 (2021).

Oh, J. T. et al. Light output performance of red AlGaInP-based light emitting diodes with different chip geometries and structures. Opt. Express 26 , 11194–11200 (2018).

Shen, Y. C. et al. Auger recombination in InGaN measured by photoluminescence. Appl. Phys. Lett. 91 , 141101 (2007).

Wong, M. S. et al. High efficiency of III-nitride micro-light-emitting diodes by sidewall passivation using atomic layer deposition. Opt. Express 26 , 21324–21331 (2018).

Han, S. C. et al. AlGaInP-based Micro-LED array with enhanced optoelectrical properties. Optical Mater. 114 , 110860 (2021).

Wong, M. S. et al. Size-independent peak efficiency of III-nitride micro-light-emitting-diodes using chemical treatment and sidewall passivation. Appl. Phys. Express 12 , 097004 (2019).

Ley, R. T. et al. Revealing the importance of light extraction efficiency in InGaN/GaN microLEDs via chemical treatment and dielectric passivation. Appl. Phys. Lett. 116 , 251104 (2020).

Moon, S. W. et al. Recent progress on ultrathin metalenses for flat optics. iScience 23 , 101877 (2020).

Arbabi, A. et al. Efficient dielectric metasurface collimating lenses for mid-infrared quantum cascade lasers. Opt. Express 23 , 33310–33317 (2015).

Yu, N. F. et al. Light propagation with phase discontinuities: generalized laws of reflection and refraction. Science 334 , 333–337 (2011).

Liang, H. W. et al. High performance metalenses: numerical aperture, aberrations, chromaticity, and trade-offs. Optica 6 , 1461–1470 (2019).

Park, J. S. et al. All-glass, large metalens at visible wavelength using deep-ultraviolet projection lithography. Nano Lett. 19 , 8673–8682 (2019).

Yoon, G. et al. Single-step manufacturing of hierarchical dielectric metalens in the visible. Nat. Commun. 11 , 2268 (2020).

Lee, G. Y. et al. Metasurface eyepiece for augmented reality. Nat. Commun. 9 , 4562 (2018).

Chen, W. T. et al. A broadband achromatic metalens for focusing and imaging in the visible. Nat. Nanotechnol. 13 , 220–226 (2018).

Wang, S. M. et al. A broadband achromatic metalens in the visible. Nat. Nanotechnol. 13 , 227–232 (2018).

Lan, S. F. et al. Metasurfaces for near-eye augmented reality. ACS Photonics 6 , 864–870 (2019).

Fan, Z. B. et al. A broadband achromatic metalens array for integral imaging in the visible. Light.: Sci. Appl. 8 , 67 (2019).

Shi, Z. J., Chen, W. T. & Capasso, F. Wide field-of-view waveguide displays enabled by polarization-dependent metagratings. In Proc. SPIE 10676, Digital Optics for Immersive Displays (SPIE, Strasbourg, France, 2018).

Hong, C. C., Colburn, S. & Majumdar, A. Flat metaform near-eye visor. Appl. Opt. 56 , 8822–8827 (2017).

Bayati, E. et al. Design of achromatic augmented reality visors based on composite metasurfaces. Appl. Opt. 60 , 844–850 (2021).

Nikolov, D. K. et al. Metaform optics: bridging nanophotonics and freeform optics. Sci. Adv. 7 , eabe5112 (2021).

Tamir, T. & Peng, S. T. Analysis and design of grating couplers. Appl. Phys. 14 , 235–254 (1977).

Miller, J. M. et al. Design and fabrication of binary slanted surface-relief gratings for a planar optical interconnection. Appl. Opt. 36 , 5717–5727 (1997).

Levola, T. & Laakkonen, P. Replicated slanted gratings with a high refractive index material for in and outcoupling of light. Opt. Express 15 , 2067–2074 (2007).

Shrestha, S. et al. Broadband achromatic dielectric metalenses. Light.: Sci. Appl. 7 , 85 (2018).

Li, Z. Y. et al. Meta-optics achieves RGB-achromatic focusing for virtual reality. Sci. Adv. 7 , eabe4458 (2021).

Ratcliff, J. et al. ThinVR: heterogeneous microlens arrays for compact, 180 degree FOV VR near-eye displays. IEEE Trans. Vis. Computer Graph. 26 , 1981–1990 (2020).

Wong, T. L. et al. Folded optics with birefringent reflective polarizers. In Proc. SPIE 10335, Digital Optical Technologies 2017 (SPIE, Munich, Germany, 2017).

Li, Y. N. Q. et al. Broadband cholesteric liquid crystal lens for chromatic aberration correction in catadioptric virtual reality optics. Opt. Express 29 , 6011–6020 (2021).

Bang, K. et al. Lenslet VR: thin, flat and wide-FOV virtual reality display using fresnel lens and lenslet array. IEEE Trans. Vis. Computer Graph. 27 , 2545–2554 (2021).

Maimone, A. & Wang, J. R. Holographic optics for thin and lightweight virtual reality. ACM Trans. Graph. 39 , 67 (2020).

Kramida, G. Resolving the vergence-accommodation conflict in head-mounted displays. IEEE Trans. Vis. Computer Graph. 22 , 1912–1931 (2016).

Zhan, T. et al. Multifocal displays: review and prospect. PhotoniX 1 , 10 (2020).

Shimobaba, T., Kakue, T. & Ito, T. Review of fast algorithms and hardware implementations on computer holography. IEEE Trans. Ind. Inform. 12 , 1611–1622 (2016).

Xiao, X. et al. Advances in three-dimensional integral imaging: sensing, display, and applications [Invited]. Appl. Opt. 52 , 546–560 (2013).

Kuiper, S. & Hendriks, B. H. W. Variable-focus liquid lens for miniature cameras. Appl. Phys. Lett. 85 , 1128–1130 (2004).

Liu, S. & Hua, H. Time-multiplexed dual-focal plane head-mounted display with a liquid lens. Opt. Lett. 34 , 1642–1644 (2009).

Wilson, A. & Hua, H. Design and demonstration of a vari-focal optical see-through head-mounted display using freeform Alvarez lenses. Opt. Express 27 , 15627–15637 (2019).

Zhan, T. et al. Pancharatnam-Berry optical elements for head-up and near-eye displays [Invited]. J. Optical Soc. Am. B 36 , D52–D65 (2019).

Oh, C. & Escuti, M. J. Achromatic diffraction from polarization gratings with high efficiency. Opt. Lett. 33 , 2287–2289 (2008).

Zou, J. Y. et al. Broadband wide-view Pancharatnam-Berry phase deflector. Opt. Express 28 , 4921–4927 (2020).

Zhan, T., Lee, Y. H. & Wu, S. T. High-resolution additive light field near-eye display by switchable Pancharatnam–Berry phase lenses. Opt. Express 26 , 4863–4872 (2018).

Tan, G. J. et al. Polarization-multiplexed multiplane display. Opt. Lett. 43 , 5651–5654 (2018).

Lanman, D. R. Display systems research at facebook reality labs (conference presentation). In Proc. SPIE 11310, Optical Architectures for Displays and Sensing in Augmented, Virtual, and Mixed Reality (AR, VR, MR) (SPIE, San Francisco, California, United States, 2020).

Liu, Z. J. et al. A novel BLU-free full-color LED projector using LED on silicon micro-displays. IEEE Photonics Technol. Lett. 25 , 2267–2270 (2013).

Han, H. V. et al. Resonant-enhanced full-color emission of quantum-dot-based micro LED display technology. Opt. Express 23 , 32504–32515 (2015).

Lin, H. Y. et al. Optical cross-talk reduction in a quantum-dot-based full-color micro-light-emitting-diode display by a lithographic-fabricated photoresist mold. Photonics Res. 5 , 411–416 (2017).

Liu, Z. J. et al. Micro-light-emitting diodes with quantum dots in display technology. Light.: Sci. Appl. 9 , 83 (2020).

Kim, H. M. et al. Ten micrometer pixel, quantum dots color conversion layer for high resolution and full color active matrix micro-LED display. J. Soc. Inf. Disp. 27 , 347–353 (2019).

Xuan, T. T. et al. Inkjet-printed quantum dot color conversion films for high-resolution and full-color micro light-emitting diode displays. J. Phys. Chem. Lett. 11 , 5184–5191 (2020).

Chen, S. W. H. et al. Full-color monolithic hybrid quantum dot nanoring micro light-emitting diodes with improved efficiency using atomic layer deposition and nonradiative resonant energy transfer. Photonics Res. 7 , 416–422 (2019).

Krishnan, C. et al. Hybrid photonic crystal light-emitting diode renders 123% color conversion effective quantum yield. Optica 3 , 503–509 (2016).

Kang, J. H. et al. RGB arrays for micro-light-emitting diode applications using nanoporous GaN embedded with quantum dots. ACS Applied Mater. Interfaces 12 , 30890–30895 (2020).

Chen, G. S. et al. Monolithic red/green/blue micro-LEDs with HBR and DBR structures. IEEE Photonics Technol. Lett. 30 , 262–265 (2018).

Hsiang, E. L. et al. Enhancing the efficiency of color conversion micro-LED display with a patterned cholesteric liquid crystal polymer film. Nanomaterials 10 , 2430 (2020).

Kang, C. M. et al. Hybrid full-color inorganic light-emitting diodes integrated on a single wafer using selective area growth and adhesive bonding. ACS Photonics 5 , 4413–4422 (2018).

Geum, D. M. et al. Strategy toward the fabrication of ultrahigh-resolution micro-LED displays by bonding-interface-engineered vertical stacking and surface passivation. Nanoscale 11 , 23139–23148 (2019).

Ra, Y. H. et al. Full-color single nanowire pixels for projection displays. Nano Lett. 16 , 4608–4615 (2016).

Motoyama, Y. et al. High-efficiency OLED microdisplay with microlens array. J. Soc. Inf. Disp. 27 , 354–360 (2019).

Fujii, T. et al. 4032 ppi High-resolution OLED microdisplay. J. Soc. Inf. Disp. 26 , 178–186 (2018).

Hamer, J. et al. High-performance OLED microdisplays made with multi-stack OLED formulations on CMOS backplanes. In Proc. SPIE 11473, Organic and Hybrid Light Emitting Materials and Devices XXIV . Online Only (SPIE, 2020).

Joo, W. J. et al. Metasurface-driven OLED displays beyond 10,000 pixels per inch. Science 370 , 459–463 (2020).

Vettese, D. Liquid crystal on silicon. Nat. Photonics 4 , 752–754 (2010).

Zhang, Z. C., You, Z. & Chu, D. P. Fundamentals of phase-only liquid crystal on silicon (LCOS) devices. Light.: Sci. Appl. 3 , e213 (2014).

Hornbeck, L. J. The DMD TM projection display chip: a MEMS-based technology. MRS Bull. 26 , 325–327 (2001).

Zhang, Q. et al. Polarization recycling method for light-pipe-based optical engine. Appl. Opt. 52 , 8827–8833 (2013).

Hofmann, U., Janes, J. & Quenzer, H. J. High-Q MEMS resonators for laser beam scanning displays. Micromachines 3 , 509–528 (2012).

Holmström, S. T. S., Baran, U. & Urey, H. MEMS laser scanners: a review. J. Microelectromechanical Syst. 23 , 259–275 (2014).

Bao, X. Z. et al. Design and fabrication of AlGaInP-based micro-light-emitting-diode array devices. Opt. Laser Technol. 78 , 34–41 (2016).

Olivier, F. et al. Influence of size-reduction on the performances of GaN-based micro-LEDs for display application. J. Lumin. 191 , 112–116 (2017).

Liu, Y. B. et al. High-brightness InGaN/GaN Micro-LEDs with secondary peak effect for displays. IEEE Electron Device Lett. 41 , 1380–1383 (2020).

Qi, L. H. et al. 848 ppi high-brightness active-matrix micro-LED micro-display using GaN-on-Si epi-wafers towards mass production. Opt. Express 29 , 10580–10591 (2021).

Chen, E. G. & Yu, F. H. Design of an elliptic spot illumination system in LED-based color filter-liquid-crystal-on-silicon pico projectors for mobile embedded projection. Appl. Opt. 51 , 3162–3170 (2012).

Darmon, D., McNeil, J. R. & Handschy, M. A. 70.1: LED-illuminated pico projector architectures. Soc. Inf. Disp. Int. Symp . Dig. Tech. Pap. 39 , 1070–1073 (2008).

Essaian, S. & Khaydarov, J. State of the art of compact green lasers for mobile projectors. Optical Rev. 19 , 400–404 (2012).

Sun, W. S. et al. Compact LED projector design with high uniformity and efficiency. Appl. Opt. 53 , H227–H232 (2014).

Sun, W. S., Chiang, Y. C. & Tsuei, C. H. Optical design for the DLP pocket projector using LED light source. Phys. Procedia 19 , 301–307 (2011).

Chen, S. W. H. et al. High-bandwidth green semipolar (20–21) InGaN/GaN micro light-emitting diodes for visible light communication. ACS Photonics 7 , 2228–2235 (2020).

Yoshida, K. et al. 245 MHz bandwidth organic light-emitting diodes used in a gigabit optical wireless data link. Nat. Commun. 11 , 1171 (2020).

Park, D. W. et al. 53.5: High-speed AMOLED pixel circuit and driving scheme. Soc. Inf. Disp. Int. Symp . Dig. Tech. Pap. 41 , 806–809 (2010).

Tan, L., Huang, H. C. & Kwok, H. S. 78.1: Ultra compact polarization recycling system for white light LED based pico-projection system. Soc. Inf. Disp. Int. Symp. Dig. Tech. Pap. 41 , 1159–1161 (2010).

Maimone, A., Georgiou, A. & Kollin, J. S. Holographic near-eye displays for virtual and augmented reality. ACM Trans. Graph. 36 , 85 (2017).

Pan, J. W. et al. Portable digital micromirror device projector using a prism. Appl. Opt. 46 , 5097–5102 (2007).

Huang, Y. et al. Liquid-crystal-on-silicon for augmented reality displays. Appl. Sci. 8 , 2366 (2018).

Peng, F. L. et al. Analytical equation for the motion picture response time of display devices. J. Appl. Phys. 121 , 023108 (2017).

Pulli, K. 11-2: invited paper: meta 2: immersive optical-see-through augmented reality. Soc. Inf. Disp. Int. Symp . Dig. Tech. Pap. 48 , 132–133 (2017).

Lee, B. & Jo, Y. in Advanced Display Technology: Next Generation Self-Emitting Displays (eds Kang, B., Han, C. W. & Jeong, J. K.) 307–328 (Springer, 2021).

Cheng, D. W. et al. Design of an optical see-through head-mounted display with a low f -number and large field of view using a freeform prism. Appl. Opt. 48 , 2655–2668 (2009).

Zheng, Z. R. et al. Design and fabrication of an off-axis see-through head-mounted display with an x–y polynomial surface. Appl. Opt. 49 , 3661–3668 (2010).

Wei, L. D. et al. Design and fabrication of a compact off-axis see-through head-mounted display using a freeform surface. Opt. Express 26 , 8550–8565 (2018).

Liu, S., Hua, H. & Cheng, D. W. A novel prototype for an optical see-through head-mounted display with addressable focus cues. IEEE Trans. Vis. Computer Graph. 16 , 381–393 (2010).

Hua, H. & Javidi, B. A 3D integral imaging optical see-through head-mounted display. Opt. Express 22 , 13484–13491 (2014).

Song, W. T. et al. Design of a light-field near-eye display using random pinholes. Opt. Express 27 , 23763–23774 (2019).

Wang, X. & Hua, H. Depth-enhanced head-mounted light field displays based on integral imaging. Opt. Lett. 46 , 985–988 (2021).

Huang, H. K. & Hua, H. Generalized methods and strategies for modeling and optimizing the optics of 3D head-mounted light field displays. Opt. Express 27 , 25154–25171 (2019).

Huang, H. K. & Hua, H. High-performance integral-imaging-based light field augmented reality display using freeform optics. Opt. Express 26 , 17578–17590 (2018).

Cheng, D. W. et al. Design and manufacture AR head-mounted displays: a review and outlook. Light.: Adv. Manuf. 2 , 24 (2021).

Google Scholar  

Westheimer, G. The Maxwellian view. Vis. Res. 6 , 669–682 (1966).

Do, H., Kim, Y. M. & Min, S. W. Focus-free head-mounted display based on Maxwellian view using retroreflector film. Appl. Opt. 58 , 2882–2889 (2019).

Park, J. H. & Kim, S. B. Optical see-through holographic near-eye-display with eyebox steering and depth of field control. Opt. Express 26 , 27076–27088 (2018).

Chang, C. L. et al. Toward the next-generation VR/AR optics: a review of holographic near-eye displays from a human-centric perspective. Optica 7 , 1563–1578 (2020).

Hsueh, C. K. & Sawchuk, A. A. Computer-generated double-phase holograms. Appl. Opt. 17 , 3874–3883 (1978).

Chakravarthula, P. et al. Wirtinger holography for near-eye displays. ACM Trans. Graph. 38 , 213 (2019).

Peng, Y. F. et al. Neural holography with camera-in-the-loop training. ACM Trans. Graph. 39 , 185 (2020).

Shi, L. et al. Towards real-time photorealistic 3D holography with deep neural networks. Nature 591 , 234–239 (2021).

Jang, C. et al. Retinal 3D: augmented reality near-eye display via pupil-tracked light field projection on retina. ACM Trans. Graph. 36 , 190 (2017).

Jang, C. et al. Holographic near-eye display with expanded eye-box. ACM Trans. Graph. 37 , 195 (2018).

Kim, S. B. & Park, J. H. Optical see-through Maxwellian near-to-eye display with an enlarged eyebox. Opt. Lett. 43 , 767–770 (2018).

Shrestha, P. K. et al. Accommodation-free head mounted display with comfortable 3D perception and an enlarged eye-box. Research 2019 , 9273723 (2019).

Lin, T. G. et al. Maxwellian near-eye display with an expanded eyebox. Opt. Express 28 , 38616–38625 (2020).

Jo, Y. et al. Eye-box extended retinal projection type near-eye display with multiple independent viewpoints [Invited]. Appl. Opt. 60 , A268–A276 (2021).

Xiong, J. H. et al. Aberration-free pupil steerable Maxwellian display for augmented reality with cholesteric liquid crystal holographic lenses. Opt. Lett. 46 , 1760–1763 (2021).

Viirre, E. et al. Laser safety analysis of a retinal scanning display system. J. Laser Appl. 9 , 253–260 (1997).

Ratnam, K. et al. Retinal image quality in near-eye pupil-steered systems. Opt. Express 27 , 38289–38311 (2019).

Maimone, A. et al. Pinlight displays: wide field of view augmented reality eyeglasses using defocused point light sources. In Proc. ACM SIGGRAPH 2014 Emerging Technologies (ACM, Vancouver, Canada, 2014).

Jeong, J. et al. Holographically printed freeform mirror array for augmented reality near-eye display. IEEE Photonics Technol. Lett. 32 , 991–994 (2020).

Ha, J. & Kim, J. Augmented reality optics system with pin mirror. US Patent 10,989,922 (2021).

Park, S. G. Augmented and mixed reality optical see-through combiners based on plastic optics. Inf. Disp. 37 , 6–11 (2021).

Xiong, J. H. et al. Breaking the field-of-view limit in augmented reality with a scanning waveguide display. OSA Contin. 3 , 2730–2740 (2020).

Levola, T. 7.1: invited paper: novel diffractive optical components for near to eye displays. Soc. Inf. Disp. Int. Symp . Dig. Tech. Pap. 37 , 64–67 (2006).

Laakkonen, P. et al. High efficiency diffractive incouplers for light guides. In Proc. SPIE 6896, Integrated Optics: Devices, Materials, and Technologies XII . (SPIE, San Jose, California, United States, 2008).

Bai, B. F. et al. Optimization of nonbinary slanted surface-relief gratings as high-efficiency broadband couplers for light guides. Appl. Opt. 49 , 5454–5464 (2010).

Äyräs, P., Saarikko, P. & Levola, T. Exit pupil expander with a large field of view based on diffractive optics. J. Soc. Inf. Disp. 17 , 659–664 (2009).

Yoshida, T. et al. A plastic holographic waveguide combiner for light-weight and highly-transparent augmented reality glasses. J. Soc. Inf. Disp. 26 , 280–286 (2018).

Yu, C. et al. Highly efficient waveguide display with space-variant volume holographic gratings. Appl. Opt. 56 , 9390–9397 (2017).

Shi, X. L. et al. Design of a compact waveguide eyeglass with high efficiency by joining freeform surfaces and volume holographic gratings. J. Optical Soc. Am. A 38 , A19–A26 (2021).

Han, J. et al. Portable waveguide display system with a large field of view by integrating freeform elements and volume holograms. Opt. Express 23 , 3534–3549 (2015).

Weng, Y. S. et al. Liquid-crystal-based polarization volume grating applied for full-color waveguide displays. Opt. Lett. 43 , 5773–5776 (2018).

Lee, Y. H. et al. Compact see-through near-eye display with depth adaption. J. Soc. Inf. Disp. 26 , 64–70 (2018).

Tekolste, R. D. & Liu, V. K. Outcoupling grating for augmented reality system. US Patent 10,073,267 (2018).

Grey, D. & Talukdar, S. Exit pupil expanding diffractive optical waveguiding device. US Patent 10,073, 267 (2019).

Yoo, C. et al. Extended-viewing-angle waveguide near-eye display with a polarization-dependent steering combiner. Opt. Lett. 45 , 2870–2873 (2020).

Schowengerdt, B. T., Lin, D. & St. Hilaire, P. Multi-layer diffractive eyepiece with wavelength-selective reflector. US Patent 10,725,223 (2020).

Wang, Q. W. et al. Stray light and tolerance analysis of an ultrathin waveguide display. Appl. Opt. 54 , 8354–8362 (2015).

Wang, Q. W. et al. Design of an ultra-thin, wide-angle, stray-light-free near-eye display with a dual-layer geometrical waveguide. Opt. Express 28 , 35376–35394 (2020).

Frommer, A. Lumus: maximus: large FoV near to eye display for consumer AR glasses. In Proc. SPIE 11764, AVR21 Industry Talks II . Online Only (SPIE, 2021).

Ayres, M. R. et al. Skew mirrors, methods of use, and methods of manufacture. US Patent 10,180,520 (2019).

Utsugi, T. et al. Volume holographic waveguide using multiplex recording for head-mounted display. ITE Trans. Media Technol. Appl. 8 , 238–244 (2020).

Aieta, F. et al. Multiwavelength achromatic metasurfaces by dispersive phase compensation. Science 347 , 1342–1345 (2015).

Arbabi, E. et al. Controlling the sign of chromatic dispersion in diffractive optics with dielectric metasurfaces. Optica 4 , 625–632 (2017).

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Xiong, J., Hsiang, EL., He, Z. et al. Augmented reality and virtual reality displays: emerging technologies and future perspectives. Light Sci Appl 10 , 216 (2021). https://doi.org/10.1038/s41377-021-00658-8

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LOPFORUM2023

March 13-15, 2023, Online(Webinar)

Welcome Message to our Pioneers, Distinguished Speakers, Scholars for Attending LOPFORUM2023

Dear Attendees of LOPFORUM2023

Over the past three-quarter century, the fields of photonics, optics, lasers have undergone a quantum leap. We have seen tremendous technological progress in photonics for the telecom industries, aviation; aerospace and medical communities. Information, intelligence, and data are transferred from one point to another more quickly and precisely than ever thought possible due to these recent advancements.

Optics and photonics greatly benefitted from the synergy with the telecommunications industry resulting in a number of new technologies including micro-packaging of optics components, photonics networks, micro and nano-sensors, femtosecond Bragg gratings and much more.Today a significant proportion of the world's communications are carried by fiber optic cables. Fiber optic technology has revolutionized the telecommunication market and is rapidly becoming a major player in information technology plus lasers, photonics and optics are being used in world-wide for 1000s of applications.

We are fortunate to be among the pioneers of this exciting and rapidly changing field. The technological achievements are the result of solid engineering, dedication, and innovation

This year, the organizers have assembled a series of plenary, keynote and invited presentations from distinguished members of the international will share with us their world class scientific R&D.We are looking forward to your presentation among these inventors.

Warm regards,

CEO and President of ARK International LLC,

Chairman LOPFOURUM 2023,

Developer of the Lightest Fiber Optic Cable in Aviation History,

Architect and Developer of World 1st Fiber Optic Sensor for- Rocket Engine Chairman SPIE International Conferences,

(Photonics Applications for Fiber Optic Sensors & Lasers for 8 years).

Important Dates

Abstract submission deadline.

January 18, 2023

Earlybird Registration

September 28, 2022

Standard Registration

December 31, 2022

On-spot Registration

March 13, 2023

Plenary Speakers

Alex Kazemi

Conference Chair ARK International LLC USA

Dr. Alex Kazemi a world recognized Micro Technologist, and materials scientist is the CEO and President of ARK International LLC is focusing on development of fiber optics, miniaturized fiber components, fiber optic sensors, and micro/nano technology of laser components for aviation, aerospace and space applications. He is developer of the lightest fiber optic cable in aviation history, World 1stfiber optic sensor for rocket engine, U.S. 1stfiber optic delivery system for micro welding oflaser chips, and leading-edge technologies. He is The Boeing Company Fiber Optic Architect, Associate Technical Fellow, and worked for 25 years for Boeing as well as 10 years for telecom, lasers, sensors, and MEMS industries. He also taught physics and materials science for several years at University of Southern California. Currently he is the Principal Consultant for development of new generation of fiber optics and sensors to the Boeing Company. He has authored/edited 8 books and one book chapter in the area of photonics, lasers, sensors, fiber optics, micro and nano technologies, plus published over 48 papers in International Journals and hundreds of presentations throughout of conferences and technical community's world-wide. In recent survey by "Research Gate" organization over 1000 of his peers reviewed his published papers. In 2018, 2019 and 2021 three separate International Awards were presented to him for the phenomenal presentation for his research on fiber optic sensor and lasers. He has been Chairman of SPIE International Conferences in Photonics Applications for Fiber Optic Sensors and Lasers for 8 years and Chairman, Chief Scientific Committee and Chief Editor of Excel Global International Conference on Lasers, Optics, Photonics, and Sensors in 2021.He has bestowed hundreds of recognitions, awards and patents.

Syed Murshid

Florida Institute of Technology USA

Professor Murshid is pushing the state-of-the-art in optical fiber bandwidth using hybrid optical architectures. His contributions include the addition of two new degrees of photon freedom to optical fiber multiplexing techniques, spatial domain multiplexing - also known as space division multiplexing (SDM), and orbital angular momentum (OAM) of photon-based multiplexing. Earlier publications relevant to these endeavors include Optics and Laser Technology article on SDM, FIO presentation on OAM, and SPIE paper on SDM & OAM. His current research revolves around combining these technologies for communication architectures exceeding 100Tb/s. In summary, Professor Murshid is the Inventor of SDM in Optical Fibers - US Patent US7174067B2 Inventor of OAM in Optical Fibers - US Patent US8396371B2 Awards: Named one of Florida's five most influential scientists, Florida Trend magazine, November 2004 Teacher of the Year, College of Engineering, Student Government 2000-2001 Postdoctoral Fellow, Electrical and Computer Engineering, Florida Institute of Technology, 1997-1998.

Ya-Ping Sun Sun

Clemson University USA

Dr. Sun received his B.Eng. (1982) from the Zhejiang Institute of Technology and his M.S. (1985) from the Zhejiang University, both in Hangzhou, China. He earned his Ph.D. (1989) at the Florida State University with Prof. Jack Saltiel. He was a postdoctoral fellow with Prof. Josef Michl (1989-91) and Prof. Marye Anne Fox (1991-92) at the University of Texas at Austin. He joined Clemson faculty in 1992.

Georgios E Romanos

Stony Brook University USA

Will update soon...

Xi'an Jiaotong University China

Yang Yue received the B.S. and M.S. degrees in electrical engineering and optics from Nankai University, China, in 2004 and 2007, respectively. He received the Ph.D. degree in electrical engineering from the University of Southern California, USA, in 2012. He is a Professor with the School of Information and Communications Engineering, Xi'an Jiaotong University, China. Dr. Yue's current research interest is intelligent photonics, including optical communications, optical perception, and optical chip. He has published over 200 peer-reviewed journal papers (including Science) and conference proceedings with >9,000 citations, five edited books, two book chapters, >50 issued or pending patents, >170 invited presentations (including 1 tutorial, >20 plenary and >30 keynote talks). Dr. Yue is a Senior Member of the Institute of Electronic and Electrical Engineers (IEEE). He is an Associate Editor for IEEE Access, Editor Board Member for three other scientific journals, Guest Editor for >10 journal special issues. He also served as Chair or Committee Member for >80 international conferences, Reviewer for >60 prestigious journals.

Sukhdev Roy

Dayalbagh Educational Institute India

Professor Sukhdev Roy received the B.Sc. (Hons.) Physics degree from Delhi Univ. in 1986, M.Sc. Physics from DEI, in 1988, and PhD. from IIT Delhi in1993. He joined the Dayalbagh Educational Institute in 1993, where he is at present the Head of the Department of Physics and Computer Science. He has been a Visiting Professor at many universities that include, Harvard, Waterloo, Wurzburg, Regensburg, Osaka, City University and Queen Mary University of London, TIFR, Mumbai and IISc. Bangalore. He has also been an Associate of the International Centre for Theoretical Physics, Trieste, Italy and is a Member of the Global Panel of MIT Technology Review. Prof. Roy has made significant contributions in Photonics that encompass nano-bio-photonics, silicon and neuro photonics, fiber optics, and optical computing. His experimental and theoretical research on nano-bio-photonic systems that includes low-power and high frequency optogenetic control of neural spiking, defines a new paradigm of technological convergence and innovation and opens up fascinating prospects for energy-efficient, ultrafast and low-cost all-optical information processing, sensing, energy conversion and healthcare. He has won a number of awards and fellowships that include, the, AICTE Career Award for Young Teachers in 2001, JSPS Invitation Fellowship, Japan in 2004,H.C. Shah Research Endowment Prize by Sardar Patel University in 2006, 1st IETE B.B. Sen Memorial Award in 2007, IETE-Conference on Emerging Optoelectronic Technologies Award in 2012, IETE-M. Rathore Memorial Award in 2016, the Systems Society of India's National Systems Gold Medal in 2016, and the Distinguished Alumni Award by the Dayalbagh Educational Institute in 2021. He also has been awarded seven best paper awards in international and national conferences. He has published 175 research papers in reputed journals and conference proceedings and 11 book chapters. He chaired the 8th World Conference and Expo on Nanoscience and Nanotechnology, Philadelphia, USA in 2020. He has delivered more than 100 invited talks in India and abroad that include Keynote Addresses and Plenary Talks at International Conferences that include the prestigious International Year of Light commemorative Keynote Address, at the 38th Convocation of the International Council of Academies of Engineering and Technological Sciences (CAETS), in 2015 and at the Annual Meeting of American Physical Society in 2008. He was the Guest Editor of the March 2011 Special Issue of IET Circuits, Devices and Systems Journal (UK) on Optical Computing. He is an Associate Editor of IEEE Access and is a member of the Editorial Board of Optics and Photonics Journal. He is also a Senior Member of IEEE and SPIE, and a Fellow of the Indian National Academy of Engineering, the National Academy of Sciences, India, IETE (India), and the Optical Society of India. He is listed in the recent Stanford researchers study of Top 2% in World Ranking of Scientists-2020, in Optoelectronics and Photonics.

Keynote Speakers

Brian J Soller

CTO at Luna Innovations USA

Dr. Soller has 25 years of experience in the research, development, and commercialization of guided-wave and fiber sensing systems. He joined Luna Innovations in 2002 as a research and development engineer, making significant contributions to multiple of Luna's industry-leading sensing and measurement solutions. After holding multiple technical and business leadership positions over the years he became Chief Operating Officer in 2021. In October 2022 he was named Chief Technology Officer and Executive Vice President of Corporate Development. He has multiple issued patents and dozens of journal and conference publications. He received a bachelor’s degree in mathematics and physics from the University of Wisconsin-LaCrosse and a doctoral degree from the Institute of Optics, University of Rochester.

Nooshafarin Kazemikhoo

University of New South Wales, Sydney Australia

I am an MD, Ph.D., Post Doc in Medical Laser, and Adjunct lecturer at the University of New South Wales, Sydney, Australia. I have been using photobiomodulation (PBM) for wound healing particularly nonhealing diabetic wounds and burn ulcers, since 2003. I have published 29 international papers and 2 books in this field. I have run several workshops and training courses on PBM in both academic and non-academic courses and have delivered several oral and poster presentations at international conferences.

Heinz W. Siesler

University of Duisburg-Essen Germany

Heinz Siesler is a Professor of Physical Chemistry at the University of Duisburg-Essen, Germany, with expertise in vibrational spectroscopy for chemical research, analysis and process control. He has 250+ publications (4 monographs), 2 patents (1998/2016) and received several academic awards (1994 Eastern Analytical Symposium Award (USA), 2000 Tomas Hirschfeld Award (USA), 2003 Buechi NIR Award (Germany), 2011 Science Kärcher Award (Germany), 2012 Fellow of the Society of Applied Spectroscopy (USA), 2017 Honorary Life-time Member of the Society of Applied Spectroscopy (USA)). Prior to his academic position he gained industrial experience in the R&D Department of Bayer AG, Germany. He also worked as lecturer (Wits University, Johannesburg, South Africa) and Post-Doc (University of Cologne, Germany), after receiving his PhD in Chemistry (University of Vienna, Austria). Specific research focuses in the last two decades were 1. imaging of biopolymer blend structure on the micro-/nanometer scale and 2. miniaturization of vibrational spectrometers for on-site measurements.

Boris Gramatikov

Johns Hopkins University USA

Boris Gramatikov is an Associate Professor at Johns Hopkins University, Department of Ophthalmology. He obtained his Dipl.-Ing. degree in Biomedical Engineering in Germany, and his Ph.D.in Bulgaria. He has completed a number of postdoctoral studies in Germany, Italy, and the United States. He joined the faculty of the Biomedical Engineering Department of Johns Hopkins in 1996 and has been working in the Laboratory of Ophthalmic Instrumentation Development at The Wilmer Eye Institute since 2000. His areas of expertise include electronics, optoelectronics, computers, computer modeling, signal/image processing, data analysis, instrumentation design, biophotonics, ophthalmic and biomedical optics, and polarization optics, all applied to the development of diagnostic methods and devices for ophthalmology and vision research. His team has developed a series of pediatric vision screeners. He has over 120 publications, 41 of which are in high-impact peer-reviewed journals. He serves as a reviewer and editorial board member with a number of technical and medical journals. Boris is the Director of Continuing Education of the Baltimore Section of the IEEE.

Niloy Dutta

University of Connecticut USA

Niloy Dutta is a professor of physics at the University of Connecticut, Storrs, CT. He was Director of Optoelectronic Device Research at AT&T Bell Laboratories, Murray Hill, NJ. He is a Life Fellow of the Institute of Electrical Engineers (IEEE), a Fellow of the Optical Society of America, a Fellow of the International Society of Optical Engineers (SPIE), and, a Member of the Connecticut Academy of Science and Engineering. He received the Photonics Society Distinguished Lecturer Award in 1995 and Bell Laboratories President's Award in 1997.

University of Waterloo Canada

Dayan Ban is a Professor of Nanotechnology Engineering in the Department of Electrical and Computer Engineering at the University of Waterloo. He received a B.Sc. and M.A.Sc at the University of Science and Technology of China, Hefei, China. He received a Ph.D. in Electrical and Computer Engineering from the University of Toronto, Toronto, Ontario, Canada, in 2003. During 2001-2002, he was a visiting scientist at Nortel Networks Optical Components, Ottawa, Ontario, Canada. Dr. Ban was on staff at the Institute for Microstructural Sciences of the National Research Council, Ottawa, from Sept. 2002 to Oct. 2005. He was a visiting scientist with the Research Lab of Electronics at MIT in 2009. Dr. Ban is a senior member of IEEE/LEOS and a registered Professional Engineer in Ontario. He has over 20 years experience in designing, fabricating, and characterizing optoelectronic devices as well as in scanning probe microscopy technique. Dr. Ban has authored or co-authored over 240 papers in refereed journals and conference proceedings and has contributed 2 book chapters and 12 patents/patent applications.

Stephen James

Cranfield University UK

Professor Stephen James leads the optical fibre sensors research theme within the Centre for Engineering Photonics at Cranfield University, UK. He undertook his PhD at the University of Southampton, studying optical phase conjugation in photorefractive materials, and joined Cranfield University in 1993 as a post-doctoral researcher to develop 3D laser velocimetry instrumentation. As his academic career at Cranfield progressed, he worked on a number of optical measurement techniques, including speckle interferometry and optical fibre sensors. His current work encompasses the development, design and application of optical fibre-based sensors and instruments for sensing physical and chemical measurands, with a strong focus on their practical deployment. The instrumentation and sensors designed by the Centre have been field trialled in applications including flight testing on fixed-wing aircraft and rotorcraft, tramway component health monitoring, composite material production process monitoring, foundation pile characterisation, and measurements of transient loading in superconducting magnets.

Mario F S Ferreira

University of Aveiro Portugal

Mario F. S. Ferreira graduated in Physics from the University of Porto, Portugal, and received the Ph.D. degree in Physics in 1992 from the University of Aveiro, Portugal, where he is now a Professor at the Physics Department. Between 1990 and 1991 he was at the University of Essex, UK, performing experimental work on external cavity semiconductor lasers and nonlinear optical fiber amplifiers. His research interests have been concerned with the modelling and characterization of multi-section semiconductor lasers for coherent systems, quantum well lasers, optical fiber amplifiers and lasers, soliton propagation, polarization and nonlinear effects in optical fibers. He is actually the leader of the Optics and Optoelectronics Group of the I3N-Institute of Nanostructures, Nano modelling and Nanofabrication. He has written about 400 scientific journal and conference publications, and several books, namely: Optics and Photonics (Lidel, 2003, in Portuguese), Topics of Mathematical Physics (Editora Ciência Moderna, 2018, Brazil, in Portuguese), Optical Fibers: Technology, Communications and recent Advances (Ed., NOVA Science Publishers, 2017), Advances in Optoelectronic Technology and Industry Development (CRC Press, 2019), Nonlinear Effects in Optical Fibers (John Wiley & Sons, OSA, 2011) and Optical Signal Processing in Highly Nonlinear Fibers (CRC Press, 2020). He was the Guest Editor of four Special Issues of Fiber and Integrated Optics (Taylor & Francis): Fiber Optics in Portugal (2005), Nonlinear Fiber Optics (2015), Optical Fiber Sources and Amplifiers (2020) and Quantum Communications (2020), a joint Special Issue of Optics Express and Applied Optics (OSA) on Optical Sensors and Sensing 2019, and a Special Issue of Fibers (MDPI) on Optical Fiber Communications (2020). He is a Senior Member and a Travelling Lecturer of both of the Optical Society of America (OSA) and SPIE - The International Society for Optical Engineering, He served in various committees of OSA and of SPIE, as well as in the organizing and scientific committees of various international conferences. Actually, he serves also as an Associate Editor or as an Advisor Board Member of several international journals in the area of optics and photonics.

Ali Masoudi

University of Southampton UK

Dr. Ali Masoudi is a senior research fellow at the Optoelectronics Research Centre (ORC) at the University of Southampton and leads the distributed optical fiber sensing group at the ORC. He received his Ph.D. in 2015 for his work on distributed acoustic sensors. After receiving his Ph.D., Dr. Masoudi designed and developed portable DAS units which he subsequently used in several industrial collaborations with entities such as Network Rail, BT, and Carbon trust. The DAS unit has also been used in several interdisciplinary collaborations with other research institutes such as the National Physical Laboratory (NPL), the Institute of Sound and Vibration Research (ISVR), and the National Oceanography Centre (NOC). So far, he has secured more than £2.5m of research funding as PI/Co-I/Research Co-I from various research councils and industrial partners. He has authored 3 patents, published more than 60 papers in scientific journals and international conferences, and has presented his research as an invited and keynote speaker on 7 different occasions. He is currently a guest editor for a special issue of Sensors Journal and serving as a member of the Technical Program Committee for Optica Sensing Congress.

Holon Institute of Technology (HIT) Israel

Dror Malka received his BSc and MSc degrees in electrical engineering from the Holon Institute of Technology (HIT) in 2008 and 2010, respectively, in Israel. He also completed a BSc degree in Applied Mathematics at HIT in 2008 and received his Ph.D. degree in electrical engineering from Bar-Ilan University (BIU) in 2015, Israel. Currently, he is a Senior Lecturer in the Faculty of Engineering at HiT. His primary research fields are nanophotonics, super-resolution, silicon photonics, and fiber optics. He has published around 50 refereed journal papers and 50 conference proceedings papers.

Dalian University of Technology China

Prof. Jiang GUO is currently a professor and doctoral supervisor at the Dalian University of Technology. He received his Ph.D. from The University of Tokyo in 2013. After graduation, he joined RIKEN as a researcher. In October 2015, he became a scientist at A*STAR (Agency for Science, Technology, and Research). He has been actively engaged in developing and applying new optical aspheric and microstructure grinding and polishing processes for over a decade. He has published more than 80 journal papers in the top journals in the fields of manufacturing, optics, precision instrumentation, material processing, and electrochemistry. He holds more than 50 international and national invention patents. He presided over more than 20 projects, such as the Japan Society for the Promotion of Science (JSPS) Youth Fund, the General Program of the National Natural Science Foundation of China, and the National Key Research and Development Program. He has won more than 10 academic awards, such as the Revitalization Award of the Japan Machine Tool Promotion Association and the Outstanding Research Achievement Award of the Chinese Students Association in Japan. He is currently a senior member of the Chinese Mechanical Engineering Society, a member of the European Society for Precision Engineering and Nanotechnology (EUSPEN), the American Society for Precision Engineering (ASPE), and the Asian Society for Precision Engineering and Nanotechnology (ASPEN), etc. He is also the reviewer for over 50 SCI journals. He serves on the editorial board and youth editorial board of several international journals and as a reviewer for over 50 international journals.

Invited Speakers

Jose Marques-Hueso

Heriot-Watt University UK

Dr. Jose Marques-Hueso is an associate professor at Heriot-Watt University, Edinburgh, UK. His research focuses on the use of optical materials, laser manufacturing, spectral conversion, and engineering applications. He received his MSc in physics from the University of Valencia and he completed his Ph.D. at the Institute of Materials Science of the UV, on the development of nanophotonic and plasmonic devices. In 2011, he joined Heriot-Watt University as a research associate and obtained a position as an assistant professor in 2017. He has been an associate professor since 2021. He has led public and industrially funded projects and carried out consultancy for laser manufacturing processes. He has published over 80 publications.

Mario De Cesare

Italian Aerospace Research Center Italy

Prof. M. De Cesare, Ph.D., is a Senior Researcher in Applied Physics at CIRA (Italian Aerospace Research Centre) and a Professor in Aerospace Physics Methodologies at the University of Campania "Luigi Vanvitelli". He is also PM&SEM in Novel Physics Methodologies for Aerospace Applications and an SEM in Airborne-gamma measurements for Natural and Anthropogenic Environmental Monitoring. His principal applications are based on the development of novel technologies for material and plasma applications in the re-entry vehicle phases. The Diagnostic Methodologies and Measurement Techniques Division at CIRA tests innovative structures for space re-entry vehicles and sustained hypersonic flight and for aeronautical subjected to high thermal gradients. It develops and perfects advanced experimental methods and tools: IR-thermography technique, Spectroscopy, Laser, and Ion Beam Analysis applications. The laboratory carries out its tests in two large CIRA facilities, the SCIROCCO and GHIBLI plasma wind tunnels, which simulate the extreme conditions encountered during space re-entries and hypersonic flight. This allows the laboratory to validate newly developed design methods and to study very advanced TPS material.

Katerina Lazarova

Institute of Optical Materials and Technologies, "Acad. J. Malinowski" Bulgaria

Assoc. Prof. Dr. Katerina Lazarova has been a scientist at the Bulgarian Academy of Sciences for the last 9 years. In 2013 she began her doctorate in the field of photonic crystals and optical sensors based on zeolites and porous materials. In 2016 she became a chief assistant at the IOMT-BAS and from 2019 to 2021 was a postdoctoral fellow with a scholarship in the same field. Currently, Dr. Lazarova is an Associate professor. Author of more than 40 articles, with awards for presentations in scientific forums and participation in numerous scientific projects in collaboration with other scientific organizations.

Gita Revalde

University of Latvia Latvia

Gita REVALDE - Dr.Phys., professor, Institute of Technical Physics, Riga Technical University, a leading researcher at the Institute of Atomic Physics and Spectroscopy of the University of Latvia. Directions of scientific research: atomic physics, quantum physics, ion physics, low-temperature plasma, determination of volatile organic compounds and heavy metal pollution in the environment, disinfection using UV, light sources, methods: laser spectroscopy, mathematical modeling, CRDS, TDLAS. Currently, studies are being conducted for the determination of VOCs in air and exhalation, in the development of UV light sources for disinfection and other applications. The experience of a project manager, supervisor, and chief executor in about 20 projects: National Research Programmes (NextICT), COVID-19 mitigation, ECOSOC, ESF, ERDF, and ERASMUS projects, managed and monitored large-scale infrastructure projects. Administrative experience as director of the Higher Education Department of the Ministry of Education and Science (2007-2012), rector of Vent spills University of Applied Sciences (2013-2016), deputy rector of Riga Technical University (2013), director of the Latvian Council of Science (2020), and president of the Almaty University of Telecommunication and Energy. Expert of the Agency "Independent Agency for Accreditation and Rating", expert of the Latvian Council of Science "Physics and Astronomy", expert of the Serbian Council of Science, member of the Latvian Physics Society, and member of the Latvian Union of Scientists.

Nikos Malliaropoulos

Sports Clinic, Mile End Hospital, Bart's, and the London UK

Dr. Nikos Malliaropoulos is a Consultant in Sports and Exercise Medicine based at the Sports Clinic Barts and the London and a Senior Clinical Lecturer at QMUL Centre of Sports and Exercise Medicine Academic Department. He has been Director of the Sports injuries clinic of the Track and Field Hellenic Association in Thessaloniki, from 1986 - 2019 and was Chief Medical Officer of the Hellenic Olympic Team XXVIII Athens Olympics 2004. Additionally, Nikos was Director of the Medical Services of the First South Eastern European Games 2007. He is a Fellow of the UK Faculty of Sports and Exercise Medicine Royal College of Surgeons Edinburgh. He is a Founding member of the European College of Sports and Exercise Physicians - ECOSEP and current Secretary in General, a Fellow of the International Federation of Sports Medicine FIMS, and a Member of the British Sports and Exercise medicine Association-BASEM. Nikos was also a Balkan Judo Champion - 6th DAN in Judo and Aris Judo Team Head Coach. His main clinical interests are in the Diagnosis, Management, and Rehabilitation of sports injuries and musculoskeletal pathologies. One of his main areas of expertise is Hamstring and Judo Research. He has significant experience in MSK ultrasonography and interventional procedures since 2000. Special interests are all soft tissue Injuries including Hamstring and troublesome muscle Injuries, Tendon Injuries, Ankle and Knee Injuries, Bone stress Injuries, and Low back pain. His main management approaches are Specific Exercise prescription as a treatment for musculoskeletal pathologies; Ultrasound guided injections, Extra Shock Wave Therapy - ESWT, and Laser therapy for musculoskeletal pathologies.

Nicusor Iftimia

Physical Sciences Inc USA

Dr. Iftimia received his Ph.D. in Physics at the University of Bucharest, Romania, and his postdoctoral training in biomedical optics at the Wellman Center for Photomedicine MGH/Harvard Medical School. He has over twenty years of experience in research in an academic-industrial environment, leading large programs related to cancer diagnosis and therapy guidance. His technical expertise is in optical imaging and spectroscopy, focusing on technology development, image analytics, and automated image analysis through machine learning. He has industry experience, transitioning projects from idea to prototype to the product through thorough project planning and execution. He works with clinicians from various hospitals across the US and Europe, performing preclinical and clinical translational research. Dr. Iftimia is the author of over 100 peer-review publications, several book chapters, and the main editor of a book. In recognition of his contribution to the biomedical optics field, Dr. Iftimia was elected as an OSA fellow in 2017 and an SPIE fellow in 2021.

Mircea Mujat

Mircea Mujat received his Ph.D. at the University of Central Florida, College of Optics and Photonics in 2004. He continued his activity as a Research Fellow with Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, and is currently a Principal Research Scientist with Physical Sciences, Inc. His current research interests include high-resolution optical imaging (i.e., optical coherence tomography, optical frequency domain imaging, adaptive optics, phase contrast imaging, confocal and polarization microscopy), polarized light scattering, and biomedical applications of lasers.

Giglio Marilena

University of Bari Italy

Dr. Marilena Giglio studied Physics at the University of Bari, Italy, and graduated with an MS in 2014 (cum laude) and a Ph.D. in 2019. In 2012 she visited the group of Prof. van Leeuwen at the Academic Medical Center of Amsterdam, The Netherlands as a trainee. In 2016 she joined Prof. Tittel's group of visiting Researchers at Rice University, Texas. After a 2-year Post-Doc at the Polytechnic of Bari, Italy she's currently an Assistant Professor in the same institution. She has published 34 research articles (Scopus), 1 review, 1 book chapter, and more than 30 proceedings. She co-invented 1 patent.

China Academy of Engineering Physics China

Associate research fellow, Research Center of Laser Fusion, China Academy of Engineering Physics. Graduated in Engineering Physics from Tsinghua University, Beijing, China. The objectives of his research are (Ⅰ) to understand assembly, installation, and integration of large laser facility, (Ⅱ) to develop key processes and tools forming the foundation for High Power Laser Facility’s long-term LRU production and maintenance strategy, and (Ⅲ) to explore multi-step alignments and close-loop of "assembly-measurement -adjustment".

Oomman K. Varghese

University of Huston USA

Oomman K. Varghese received B.Sc. and M.Sc. degrees in Physics from Mahatma Gandhi University and a Ph.D. from the Indian Institute of Technology Delhi (IITD), India. He conducted postdoctoral research in the University of Kentucky and the Pennsylvania State University and then worked as a Process Development Engineer in First Solar, USA. He is currently an Associate Professor and Chairman of the Graduate Program in the Department of Physics, University of Houston (UH), Texas. His group's research primarily aims to develop nanoscale materials and heterostructures and investigate their unique properties for solar energy conversion and medical applications. He has contributed to over 110 peer-reviewed articles, one book, two book chapters, and three patents. His publications have received over 37,000 citations (Google Scholar h-index - 74). In 2011, Thomson Reuters ranked him 9th among 'World's Top 100 Materials Scientists' in the past decade. In 2014, 2015, and 2016 he received the title 'Highly Cited Researcher' and had his name listed in Thomson Reuters' World's Most Influential Scientific Minds. He is a recipient of the UH College of Natural Science and Mathematics John C. Butler Award for Excellence in Teaching. He is among the top 2% of scientists in the world per the Stanford University Report, 2020.

Andrea Zifarelli

Andrea Zifarelli received the M.S. degree (cum laude) in Physics in 2018 from the University of Bari and his Ph.D. in Physics from the University of Bari in 2022. His research activities were mainly focused on the development of spectroscopic techniques based on laser absorption for the analysis of complex gas mixtures by employing quartz tuning forks as sensitive elements. This investigation was performed by using innovative laser sources as well as developing new algorithms for multivariate analysis approaches. Currently, his research activities are carried out at the PolySenSe Lab, a joint-research laboratory between the Technical University of Bari and THORLABS GmbH.

Ella Faktorovich

University of California, Berkeley USA

Dr. Faktorovich has authored multiple peer-reviewed research publications, book chapters, and books on laser eye surgery and laser physics, including the definitive textbook on the use of femtosecond laser technology in all-laser LASIK or IntraLASIK. The book has been reviewed in the American Journal of Ophthalmology and received praise from fellow surgeons as “a necessary book to read for any refractive surgeon”. Dr. Faktorovich is the founder and remains the Chair of the Annual San Francisco Cataract, Cornea, and Refractive Surgery Symposium dedicated to continuing education of the Bay Area eye doctors in refractive surgery and other aspects of advanced patient eye care. Dr. Faktorovich is the Founding Director of Pacific Vision Institute. Under her leadership, Pacific Vision Institute brings the latest advances in laser technology to patients and trains physicians in laser applications to eye surgery.

UC Santa Barbara USA

Lei Wang is currently a Ph.D. student at UC Santa Barbara. Lei Wang graduated from Shandong University (China) with a bachelor's degree in Physics in 2014. After that, he continued his graduate studies at Shandong University and the Institute of Semiconductors, Chinese Academy of Sciences, where he focused on developing high power quantum cascade lasers (QCLs), including semi-insulating InP regrowth and phase-locked arrays of QCLs. He joined the UCSB iPL in 2017 as a Ph.D. student. He is focusing on QD laser development and laser integration for silicon photonics.

Hrishikesh Das

Pacific Northwest National Laboratory USA

Dr. Hrishikesh Das is Materials Scientist at Applied Materials & Manufacturing, Pacific Northwest National Laboratory, Richland, Washington, USA. He has more than 11 years of experience in Solid Phase Joining Processes. His research interests are mainly focused on Friction Stir Welding/Processing and allied solid phase processes/extrusion (ShAPE). He has published over 55 research articles in reputed international journals and is credited with couple of patents.

Qiurong Yan

Nanchang University China

Qiurong Yan received the B.S. degree from the University of Electronic Science and Technology of China in 2005, the M.S. and Ph. D. degree from University of Chinese Academy of Sciences in 2008 and 2012, respectively. He is a professor with school of information engineer, Nanchang University, and a winner of Outstanding Young Talents Project in Jiangxi Province. His research interests include underwater wireless optical communication, photon counting wireless communication, single photon imaging, and computational imaging. He has published more than 60 SCI and EI papers in important journals and academic conferences, including 5 top journals. As the first inventor, he authorized more than 20 invention patents. He participated in the formulation of 1 industry standard, participated in the organization of 5 domestic and foreign academic conferences, and gave more than 10 invited reports. He is a reviewer for high-level international journals such as Applied Physics Reviews, Optics Express, Optics Letters, etc.

Ivo Rendina

National Research Council Italy

Ivo Rendina (Italy, 1960) is the director of the Institute of Applied Sciences and Intelligent Systems“Eduardo Caianiello” (ISASI) of the Italian National Research Council (CNR). He also teaches optoelectronics at the University of Calabria (Italy) and at the Universidad de San Francisco de Quito in Ecuador. He is past-president of the SocietàItaliana di Ottica e Fotonica (SIOF), Italian branch of the European Optical Society (EOS), EOS fellow, CNR representative in the Union Radio Scientifique Internationale (URSI), chair of the Advisory Council for Aeronautics Research in Europe (ACARE), chair and organizer of several international conferences, such as the series of EOS Topical Meetings on Optical MicroSystems (since 2005) and the series of Optics+Optoelectronics SPIE Conferences (since 2013). He has been responsible or coordinator of more than 35 Italian and international projects or research contracts with industry, holds 9 patents, has authored or co-authored more than 300 publications, and has given more than 20 invited and plenary talks at scientific conferences in the field of photonics, optical microsensors, and microsystems. Scopus: h-index 41, citations 4899; Google scholar: h-index 47, citations 6440.

Zhejiang University China

Professor Chen is with College of Optical Science & Engineering, Zhejiang University, China. He has authored tens of peer-reviewed research publications on optical instrumentation and communication. He is good at the combination of scientific research and practical application. He has professional software and hardware design skills and rich enterprise experience. Now, he works at deterministic networking for remote control of industrial machines, optometry and ophthalmic equipment.

Rogerio Nogueira

Will be Update Soon...

Neda Ghofraniha

National Council of Research Italy

Neda Ghofraniha is a researcher at Istituto dei Sistemi Complessi (Consiglio Nazionale delle Ricerche) in Italy and currently working in the fields of random photonics and microlasers. She has consolidated experience in nonlinear optics and nonlinear waves propagation and past experience in phase transitions in soft matter. Her main achievements are the first observation of nonlocal dispersive optical shock waves in liquids and the first experimental demonstration of the Replica Symmetry Breaking Theory, that is mentioned in the motivations of the Nobel Prize in Physics 2022 to Giorgio Parisi. In addition, she realized several micron-sized lasers made of biomimetic and lithographed organic materials, liquid droplets, and electrospun polymer fibers.

Francesco De Martini

Sapienza University Italy

Francesco De Martini: The personal profile is that of a person who has reached a considerable age in good health and who intends to continue by deliberately adhering to an intention of decency and honesty by putting in place all the resources of intelligence and culture of which he has so far come, or will come. In possession, Science, in particular modern cosmology, as well as the continuous (and tiring!) Study of the piano (started at the age of five) is at the centre of his interests. Precisely, on the latter front, Federico Chopin and Roberto Schumann are the inspiring geniuses of the moment: Then who knows…

Thinhinane AOUDJIT

University of Technologies of Troyes France

Dr. AOUDJIT Thinhinane is currently a postdoctoral fellow at the University of Technologies of Troyes in the Grand Est region of France. She obtained her first master degree at the University of Science and Technology of Algiers (USTHB) in fundamental physics specializing in radiation-matter interaction. Then, she obtained in 2018 her second degree in optical and photonic engineering from the Science Sorbonne University in Paris. Following this diploma, Thinhinane joined the Light, nanomaterials, nanotechnologies (L2n - CNRS-EMR 7004) team of the University of Technology of Troyes for a PhD thesis on near-field photochemical imaging of chiral nanostructures. During her thesis, she worked a lot with different lasers like Ti:Sa for the irradiation of her samples.

Rong-Jun Xie

Xiamen University China

Rong-Jun Xie obtained his PhD in Inorganic Non-metallic Materials at Shanghai Institute of Ceramics, Chinese Academic of Science in 1998. After carrying out post-doctoral work at National Institute for Materials Science (NIMS, Japan), National Institute for Advanced Industrial Science and Technology (AIST, Japan), and Alexander von Humboldt (AvH) research fellow at Darmstadt University of Technology (Germany), Xie joined National Institute for Materials Science (NIMS) as a Senior Researcher in 2003, and was promoted to Principal Researcher in 2007 and to Chief Research in 2017. In 2018, he moved to Xiamen University as a full professor at College of Materials. Xie's research interests include (i) phosphors for lighting and displays; (ii) mechanoluminescent materials for sensing technologies; and (iii) quantum dots and emissive displays. He has contributed to over 280 published papers and over 70 invited talks, and held 45 patents.

Yiwei Dong.Ph.D. Associate Professor. Currently Dr. Dongis an Associate Professor of Mechanical & Materials Engineering at the Xiamen University, Xiamen, China, where he directs the Advanced Manufacturing Lab (AML), He has more than 10 years of research experience focus on the Advanced Manufacturing Technology, Multi-scale modelling of heat and mass transfer for materials processing, Intelligent and adaptive control of manufacturing processes, etc., He has (co)authored over 10 conference papers, 10 patents, and approximately 50 articles, chapters, proceedings, and reports.

Isaac Y August

Shamoon College of Engineering Israel

My research is in the field of computational optics and computational imaging with computational spectroscopy. Computational Optics is a subfield in electrical engineering that lays down principles for computational measurement and the acquisition of information about phenomena involving the interaction of light and matter. This field can be harnessed for very advanced applications in different scopes: Imaging, Spectroscopy, Flight Time Measurement (LiDAR), and many other applications. Designing a system based on computational optics relies on carefully designed, advanced optical and electro-optical components along with using integration and application of state-of-the-art mathematical theories. In my research, we develop and design optical and electro-optical components for computational sensing systems. The electro optical components can be built on interference components in micro resonators, coded aperture, waveguide and optical fibers, diffraction grating etc. These components can be combined with each other to obtain a component that best suits its task. The purpose of these components is to enable indirect measurement, as well as multiplication measurement. In addition to hardware development, different types of algorithms are designed and implemented to realize a complete sensing system.

Estefania Hernandez-Martin

University of La Laguna Spain

Estefania Hernandez-Martin works at the University of La Laguna as researcher awarded by EU Next Generation. She received her Ph.D. degree in 2018 focused on neuro imaging techniques in the human brain. Her experticity is in the optical field, developing a new approach in the data processing for diffuse optical imaging compared with functional magnetic resonance imaging. Also, she has been working as research associate in both the University of California, Irvine and University of Southern California developing and optimizing algorithms to electrophysiological data sets. Her research focuses on signal processing, modelling, multivariate statistics and data interpretation for both electrophysiological and neuro imaging data sets that help to explain the behaviour of the brain.

Nanyang Technological University Singapore

Dr Yu Luo is an associate professor in the School of Electrical and Electronic Engineering at Nanyang Technological University (NTU). He received his PhD in Physics from Imperial College London in 2012 and joined NTU as an assistant professor in 2015, where he was promoted to an associate professor in 2021. Prof. Luo's research interests focus on the design of metamaterials and plasmonics from fundamental aspects to various practical applications. His recent work has results in a number of high-impact journal publications in Science, Nature Physics, PNAS and PRL and has been highlighted by many scientific magazines and public media, including Nature Photonics, Nature Physics, Physics World, Phys.org, BBC News, Guardian, etc. Associate Professor, School of Electrical & Electronic Engineering Deputy Director, Centre for OptoElectronics and Biophotonics (COEB), School of Electrical and Electronic Engineering (EEE).

Pramod Kumar

QuantLase Lab UAE

Dr. Pramod KUMAR (M. Phil Physics & Ph.D.-Laser Tech.), is working as a Principal Scientist and Research team leader at QuantLase Imaging Laboratory, Abu Dhabi, U.A.E. Presently, he is as an ambassador at ideaXme, London, England. Recognizing the value of Laser technology for healthcare and research, Dr. Kumar championing its study and Invented of the "Laser-based DPI technology (Diffractive Phase Interferometry)", a novel advance technique used to screen and detect COVID-19 infection by examining the tiny blood samples. It allows the health authorities to carry out large-scale screening within a few seconds. Before joining QuantLase Lab, Dr. Kumar Joined AiFi Technologies LLC, UAE, where he held positions as a Senior Experimental Research Scientist- Quantum Physics (July 2019-March 2020). He started his research career with the M.Sc (Physics 1997) Degree from C.C.S University, Meerut, India and M. Phil. (Instrumentation Physics) degree from Indian Institute of Technology Roorkee(IIT-R), Roorkee, India in 2000. In 2001, he has joined as a Research Assistant at Indian Institute of Technology Bombay (IIT-B), Mumbai, India where he worked on Optical Pattern formation and self-organization in a Photonic system. Dr. Pramod Kumar earned his Ph.D. (Laser Technology) degree from School of Physical Sciences, Jawaharlal Nehru University (JNU), New Delhi, India in 2009. After completing his thesis, He has been worked as Assistant Professor in Delhi University, India from 2009 to March 2010. In April 2010, he moved to France to pursue his research work as a Post-Doctoral Fellow at LaboratoireCommun de Metrologie LNE-CNAM, Paris, Franceon the Design and Development of Signal Resonant Optical Parametric Oscillator for Imaging and for the Spectroscopic purpose. To continue further his research carrier, he has worked as Post-doctoral Research Associate (2011-2014) in Femtosecond Laser Laboratory, IISER Mohali, Punjab, India. Indian Institute of Science Education and Research Mohali' which is a premier institute in India. Dr. Pramod Kumar since January 2015 when he started his Senior Laser Research Staff tenure with Laser Physics Group at Tyndall National Institute and University College Cork, Cork, Ireland. In 2017, Dr. Kumar joined as a Disordered Photonics Research Fellow, Department of Physics and Astronomy, College of Engineering, Mathematics and Physical Sciences, University of Exeter, England, United Kingdom. He has been involving in different leadership events especially in originating various international conferences, invited lecturers, and managing well all of them. he was excellent in delivering science communication and successfully presented several talks and delivered invited lecture in various reputed academic institutions like Imperial College London, Cambridge University, Bangor University and Paris Tech, Paris etc. He was invited to visit the Andrew and Peggy Cherng Department of Medical Engineering at California Institute of Technology, Pasadena California, May 19, 2018.Dr. Kumar is a member of the Optical Society of America, American Institute of Physics, the Institute of Electrical and Electronics Engineers (IEEE), the American Physical Society and SPIE America.

Kamal Nain Chopra

Maharaja Agrasen Institute of Technology, Laser Science and Technology Centre India

Dr Kamal Nain Chopra has done B.Sc. (University of Delhi), M.Sc. (Physics - IIT, Delhi), and M.Tech. (Opto-Electronics - IIT, Delhi), and PhD (Applied Physics - IIT, Delhi). He has served DRDO for a period of 33 years and superannuated as Scientist G, from Laser Science and Technology Centre (LASTEC), Delhi, in the year 2005. Subsequently, he has also served as Professor (Physics) in NSIT (DU) and MAIT(GGSIPU), and as Project Scientist in IIT, Delhi, in various Projects, on Topics including Photonics, Thin Films, and Optical Testing. He has about 390 publications including about 330 in peer reviewed international journals (UK, USA, France, Germany, Italy, Netherlands, and China; including J.Opt.Soc. Am., APPLIED OPTICS, OPTICA ACTA, Nouvelle Revue d'Optique Appliquee, OPTIK, THIN SOLID FILMS, and Chinese JOURNAL OF PHYSICS, on various topics including Thin Films Optics, Lasers and Laser Components, Holography, and Modern Optics; 15 Invited talks; 15 Technical reports; and 30 papers in International Conference Proceedings (e.g.Taylor and Francis, UK; and Scientific Net, Switzerland). Dr Kamal Nain Chopra has co-authored a Monograph titled, "Thin Films and their Applications in Military and Civil Sectors", DESIDOC, DRDO, Ministry of Defence, INDIA, 2010. He has authored a Monograph titled, "Unconventional Lasers: Design and Technical Analysis", DESIDOC, DRDO, Ministry of Defence, INDIA, 2017. He has also authored a Book titled, "Conventional and Unconventional Sources of Renewable Energy: Renewable Energy Sources", Lambert Academic Publishing, LAP, GERMANY, 2017. In addition, he has authored a Monograph titled, "Spintronics Theoretical Analysis and Designing of Devices Based on Giant Magnetoresistance", DESIDOC, DRDO, Ministry of Defence, INDIA, 2019. His recent book titled, "Optoelectronic Gyroscopes and Applications" has been published by SPRINGER NATURE in the year 2021. He has authored a Book titled, "Novel Emerging Techniques of business management", Lambert Academic Publishing, LAP, GERMANY, 2021. He has authored another Book titled, "Optoelectronic Instrumentation for Research in Oceanography", Lambert Academic Publishing, LAP, GERMANY, 2021. Recently, he published a monograph titled, "Infrared Signatures, Sensors and Technologies" DESIDOC, DRDO, Ministry of Defence, INDIA, 2022. He has undertaken visits to foreign universities and industries including (i) School of Thin Film Coatings, Department of Physics, St. Jerome University, Marseille, FRANCE [5 months (1984-85)]; (ii) Department of Physics, Innsbruck University, Innsbruck, AUSTRIA, including 5 days in M/s. Balzers, Liechtenstein, SWITZERLAND [10 days (1995)]; and (iii) M/s. Elettrorava, Torino, ITALY [15 days (2000)]. He has vast experience serving the Recruitment and Assessment Boards of DRDO (RAC and CEPTAM), as Chairman as well an Expert Board Member. He is a Reviewer and Editorial Board Member for some leading International Journals. His fields of Specialization are Optoelectronics, Unconventional Lasers, Optical Gyroscopes, Thin Films Designing, Fabrication, and Characterization by modern Techniques, and Specialized Optical Testing Techniques.

AvazNaghipour

University College of NabiAkram Iran

Dr. Naghipour received Ph.D. degree in Applied Mathematics (Quantum Computing) from University of Tabriz, Tabriz, Iran in 2015. Now he is an Assistant Professor, Department of Computer Engineering, University College of NabiAkram, Tabriz, Iran. Dr. Naghipour has published over 20 technical papers and is the author of the book Algebraic Construction of Binary Quantum Stabilizer Codes (LAMBERT Academic Publishing Co., 2016). His research interests include image processing, pattern recognition, artificial intelligence, medical information processing, fuzzy logic, genetic algorithms, neural networks, optimization, quantum computing, and quantum information. Dr. Naghipour is a Member of the American Mathematical Society, and a Member of the Mathematical Society of Iran. Dr. Naghipour is also a Member of the Mendeley Advisor Community and a Reviewer of IEEE Communications Letters.

North-West University South Africa

BSc Physical and Chemical sciences, Hons in Applied Radiation Sciences, MSc in Applied Radiation Sciences, currently PhD in Applied Radiation Sciences (nuclear forensic SCIENCES), currently a member of South African nuclear forensic research group.

Kahouadji Badis

Abderrahmane Mira University of Bejaia Algeria

Dr. Kahouadji has a PhD in physics, option: physics of materials since April 2017, teacher-researcher at A.Mira university of Bejaia –Algeria-, faculty of technology. He is working on nanomaterials based on rare earth orthophosphates in collaboration with two laboratories: Laser Department/ Nuclear Research Centre of Algiers (CRNA), Vinča Institute of Nuclear Sciences, University of Belgrade. Since approximately 7 years his research is entirely devoted to the development of luminescent materials and scintillators for medical and nuclear applications. He has managed 4 master project as director and 1 Ph.D. thesis in progress. He has published more than 18 international papers. He is Editorial Board Member in International Journal of Materials Science and Applications (IJMSA).and Journal of Modern Polymer chemistry and Materials, Reviewer for Advances in Science, Technology and Engineering Systems Journal (ASTES). has about 6 international and 3 national oral communications. Skills and expertise: Nanomaterials Luminescent materials Photoluminescence spectroscopy Sol-Gel Synthesis Phosphors. Inorganic Scintillators. Nanocomposite Scintillators.

• Laser Applications
• Laser Science and Technology
• Laser and laser optics
• Semiconductor Lasers
• Chemical Gas Lasers
• Optical and Fibre Optical Sensors and Instrumentation
• Micro-Opto-Electro-Mechanical Systems (MOEMS)
• Optical Communications, Switching and Networks
• Optical Fiber Technology: Materials, Devices and Systems
• Quantum Optics
• Quantum Photonics and Information Technologies
• Biophotonics and Microwave photonics
• Photonic Materials and Metamaterials
• Photonic Sensors and Crystals
• Optical Materials, Characterization Methods and Techniques
• Quantum imaging
• Biomedical optics
• Applications of Nonlinear Optics
• Optoelectronic Devices
• Quantum Optics and Quantum Information
• Wave propagation
• Optical Design and Instrumentation Design
• Nano-Photonics and Nano Optics
• Fiber Optic Sensors
• Lasers and Fiber Optics
• Polarization Optics

Tentative Schedule

Event venue location info and gallery

Her are some nearby hotels

0.4 Mile from the Venue

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0.6 Mile from the Venue

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The Leading Website for the Photonics Industry: News, White Papers, Articles, Products, Directory, Events and more GoPhotonics is the leading website for the Photonics Industry. We keeps users up to date with the latest news, information on new products, upcoming events, webinars, calculators, white papers, etc.The website has created a unique product search tool that’s helps users find products based on their requirement.

ICEFORUM2023 - SPECIAL SESSION

Title: TECHNOLOGICAL INNOVATION AND NEW OPPORTUNITIES IN ENVIRONMENTAL-FRIENDLY CIVIL ENGINEERING FOR SUSTAINABLE DEVELOPMENT CONTRIBUTION

ICEFORUM2023 is an international forum to share and highlight novel developments and ideas on the fields of Infrastructure and Civil Engineering, to develop practical and sustainable solutions for current challenges. The Universities of Bologna (Italy) and Granada (Spain) is proposing a special session titled “Technological innovation and new opportunities in environmental-friendly civil engineering for sustainable development contribution” to discuss about different topics related with the session theme including the use of new materials, life cycle assessment in civil engineering or tools to support sustainable construction management.

Dr Michelle Lynch is a PhD in Chemicals and Catalysis and Fellow of the Royal Society of Chemistry (FRSC). Her 24 years of post-doctoral experience span catalyst R&D, catalyst and precious metals market research, patent analysis and consulting. She is currently the Director and Owner of Enabled Future Limited (EFL). Prior to setting up EFL, Michelle worked with IHSMarkit, Nexant and Johnson Matthey. She is a regular speaker at conferences and contributor to industry magazines. Her publications to date have included features in IHS Chemical Bulletin, IHS Quarterly, The Catalyst Review, Recycling & Waste World and The Catalyst Group Intelligence Report. She lives and runs her consultancy in West Midlands, UK. She is passionate about sustainability, pollution abatement and helping to create high impact solutions to tackle climate change.

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• Real World Experience of DILI from Hospital Report
• Criteria for Patients Selection
• Pharmacoepidemiologic Databank Preparation and Data Collection
• Drug Causality Assessment
• Assessment Tools
• Expert Opinion
• A detection algorithm for DILI

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Groundbreaking Innovations in Science and Technology in Key Industry Growth Segments Will Drive OFC 2021 Virtual Programming and Exhibition

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21 April 2021

Hundreds of virtual sessions will create a dynamic learning experience spanning the globe during one of the most anticipated events of the year

WASHINGTON – The 2021 Optical Fiber Communication Conference and Exhibition (OFC) , the premier event in telecom and optical networking and communication, will present unparalleled technical and business programming representing the entire ecosystem—from research to marketplace, during its interactive, all-virtual event, 06 – 11 June 2021.

Executives, technical experts, academia, media and analysts will connect through an international, flexible schedule and dynamic virtual platform. This format allows registrants across time zones to learn, discuss and demonstrate innovations from optical and electrical components to systems and networks.

OFC’s comprehensive programming spanning six days will be presented virtually, covering recent progress in research (near- and long-term) and technology. Content presented live will also be recorded for on-demand viewing.

“OFC continues to engage its audience year over year by presenting sessions that provide breakthrough research, expert insight and real-world examples,” said Chongjin Xie , OFC General Chair, Alibaba Group, USA . “As a global community, we are embracing the opportunity to use the optical infrastructure and communication technology developed by experts in the field as a platform for universal collaboration of our participants.”

This year’s event features a plenary session, peer-reviewed presentations and nearly 100 invited speakers, four Symposia, three Special Sessions, 10 Workshops, seven Panels, 53 Short Courses plus business-focused programming. Topics include quantum communications and machine learning in terms of network operation and how optics supports machine learning and neuromorphic computing. Free space optical communications (FSO) technology will be the focus of several presentations in addition to photonic integration, spatial division multiplexing (SDM) and 5G.

PLENARY SPEAKERS

Plenary speakers Nancy Shemwell , COO, Trilogy Networks, USA ; Young-Kai Chen , program manager, Microsystems Technology Office, Defense Advanced Research Projects Agency (DARPA), USA ; and Yiqun Cai , vice president, Alibaba Group, China will discuss edge cloud support and applications in rural territories, advances in photonics and artificial intelligence and the evolution of networking driven by cloud computing.

CONFERENCE PROGRAMMING HIGHLIGHTS:

The virtual OFC technical program will span six days allowing speakers and participants to engage in a live, interactive format.

Special conference programming includes the Symposia, Panels, the Open Networking Summit and the Demo Zone.

• Emerging Photonic Technologies and Architectures for Femtojoule per Bit Optical Networks
• On the Edge:  MEC- based Network Architectures in Support of Enterprise Cloud
• Quantum Information Science and Technology (QIST) in the Context of Optical Communications​
• The Role of Machine Learning in Optical Systems and the Role of Optics in Machine Learning Systems  
• Panelists during the Open Networking Summit “Towards Converged Open Packet-optical Networks” session will present their views on network disaggregation and how it is driving the design of new devices and technologies and debate deployment strategies and challenges in open networking.
• Deployment Challenges of 400G Optics and Beyond
• THz Communication for Beyond 5G Networks
• Challenges of Coherent Transponders Approaching the Shannon Limit
• PON Disaggregation, from SDN Abstraction to Full Virtualization. Benefits, Obstacles and Trends
• Advanced Laser Technologies in Post-100Gbaud Era
• Pros and Cons of Low-margin Optical Networks
• Is Optical Switching Finally Ready For Large-scale Deployment in Datacenters and Advanced Networks?
• The OFC Demo Zone will showcase live demonstrations of research projects and proof-of-concept implementations in the space of optical communication devices, systems, networks, including SDN/NFV as well as software tools/functions.

BUSINESS PROGRAMMING :

OFC’s vibrant business-focused programming will provide participants high-level overviews of hot topics and market trends. Sessions will address the state of the industry, emerging technologies and recommended courses of action to tackle even the toughest business challenges.

This year’s programming taking place 08 - 11 June 2021, includes Market Watch, Network Operator Summit and Data Center Summit and 25 other sessions.

• Spanning four days, the Market Watch program will feature seven panel discussions on the latest application topics and business issues in optical communications. Leading experts in their fields will participate in talks, including the much anticipated “ State of the Industry ” analyst panel.
• Service providers and network operators present their insider perspective during the Network Operator Summit . This year’s session will feature a keynote speaker and panels on 5G networks and the debate between hyper scale and co-location at the edge.
• This year’s Data Center Summit session will feature a keynote from Gaya Nagarajan , Director, Network Engineering, Facebook, USA , moderated by Loukas Paraschis ,  Infinera, USA. Two additional sessions will discuss what is next for Inter Data Center Interconnects (DCIs) and the next phase of the data center technology roadmap beyond 400G.
• Educational programs on the virtual show floor will cover market trends, new technologies and insight into the future. Hear from industry groups such as Ethernet Alliance, the European Telecommunications Standards Institute Industry Specification Group for F5G, IEEE, IEEE Future Directions, OIF, Open Eye and OpenROADM.

MEDIA REGISTRATION:  Media/analyst registration for OFC can be accessed  online .

The OFC 2021 Virtual Exhibition will feature an enhanced experience providing the greatest opportunity for exhibitors to connect with customers and demonstrate new products and solutions. View the OFC website for upcoming announcements on registration, schedule updates and more.

The 2021 Optical Fiber Communication Conference and Exhibition (OFC) is the premier conference and exhibition for optical communications and networking professionals. For more than 40 years, OFC has drawn attendees from all corners of the globe to meet and greet, teach and learn, make connections and move business forward. OFC includes dynamic business programming, an exhibition of global companies and high impact peer-reviewed research that, combined, showcase the trends and pulse of the entire optical networking and communications industry. OFC is co-sponsored by IEEE Communications Society (IEEE/ComSoc), IEEE Photonics Society, The Optical Society (OSA) and managed by OSA. OFC 2021, an all-virtual event, will take place 06 – 11 June 2021. Follow @OFCConference, learn more at OFC Community LinkedIn , and watch highlights on OFC YouTube .

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