Breaking the in-coupling efficiency limit in waveguide-based AR displays with polarization volume gratings

Area of Science:

• Optics and Photonics
• Display Technology
• Spatial Computing

Background:

• Waveguide-based augmented reality (AR) displays offer a slim form factor and high optical performance for spatial computing and metaverse applications.
• Existing waveguide combiners suffer from low optical efficiency and poor image uniformity, limiting user experience.
• Polarization volume gratings (PVGs) are key components in these displays.

Purpose of the Study:

• To analyze the root causes of low optical efficiency and poor uniformity in waveguide-based AR displays.
• To discover and leverage an anomalous polarization conversion phenomenon in PVGs.
• To improve the performance of next-generation AR displays.

Main Methods:

• Analysis of optical efficiency and uniformity in waveguide-based AR displays.
• Investigation of polarization conversion in PVGs under non-Bragg conditions.
• Experimental measurement of light leakage in PVGs using laser sources and LCoS light engines.
• Simulation of a waveguide display with a 50° field of view.

Main Results:

• An anomalous polarization conversion phenomenon in PVGs was discovered and experimentally verified.
• This phenomenon was leveraged to overcome the trade-off between in-coupling efficiency and eyebox uniformity.
• Simulations showed a 2x improvement in in-coupling efficiency and a 2.3x improvement in uniformity using first-order polarization conversion in PVGs compared to conventional couplers.

Conclusions:

• The anomalous polarization conversion in PVGs is a viable method to enhance AR display performance.
• This discovery can significantly improve efficiency and uniformity in next-generation waveguide-based AR systems.
• The findings pave the way for more immersive and user-friendly AR experiences.