Metasurfaces for near-eye display applications

Virtual reality(VR)and augmented reality(AR)are revolutionizing our lives.Near-eye displays are crucial technologies for VR and AR.Despite the rapid advances in near-eye display technologies,there are still challenges such as large field of view,high resolution,high image quality,natural free 3D effect,and compact form factor.Great efforts have been devoted to striking a balance between visual performance and device compactness.While traditional optics are nearing their limitations in addressing these challenges,ultra-thin metasurface optics,with their high light-modulating capabilities,may present a promising solution.In this review,we first introduce VR and AR near-eye displays,and then briefly explain the working principles of light-modulating metasurfaces,review recent developments in metasurface devices geared toward near-eye display applications,delved into several advanced natural 3D near-eye display technologies based on metasurfaces,and finally discuss about the remaining challenges and future perspectives associated with metasurfaces for near-eye display applications.

Breaking the optical efficiency limit of virtual reality with a nonreciprocal polarization rotator

A catadioptric lens structure,also known as pancake lens,has been widely used in virtual reality(VR)displays to reduce the formfactor.However,the utilization of a half mirror(HM)to fold the optical path thrice leads to a significant optical loss.The theoretical maximum optical efficiency is merely 25%.To transcend this optical efficiency constraint while retaining the foldable characteristic inherent to traditional pancake optics,in this paper,we propose a theoretically lossless folded optical system to replace the HM with a nonreciprocal polarization rotator.In our feasibility demonstration experiment,we used a commercial Faraday rotator(FR)and reflective polarizers to replace the lossy HM.The theoretically predicted 100%efficiency can be achieved approximately by using two high-extinction-ratio reflective polarizers.In addition,we evaluated the ghost images using a micro-OLED panel in our imaging system.Indeed,the ghost images can be suppressed to undetectable level if the optics are with antireflection coating.Our novel pancake optical system holds great potential for revolutionizing next-generation VR displays with lightweight,compact formfactor,and low power consumption.

Prospects and challenges in augmented reality displays

Augmented reality(AR)displays are attracting significant attention and efforts.In this paper,we review the adopted device configurations of see-through displays,summarize the current development status and highlight future challenges in micro-displays.A brief introduction to optical gratings is presented to help understand the challenging design of grating-based waveguide for AR displays.Finally,we discuss the most recent progress in diffraction grating and its implications.