Multifunctional metasurfaces for polarisation control and beam shaping in AR/VR light engines

For augmented reality and virtual reality (AR/VR) waveguide-based head-mounted displays, the light engine critically determines performance, user experience, and form factor, with key requirements including compactness, high optical efficiency and brightness, high resolution, wide eyebox, wide field of view (FoV), uniform colour imagery, and low power consumption. Current AR light engines remain limited by bulky multi-element optics, restricted FoV, and inadequate brightness for outdoor use. MicroLEDs are promising light sources due to exceptional brightness, small pixel pitch, excellent optical efficiency, and compact form factor, but their unpolarised emission and wide Lambertian angular distribution cause significant coupling losses in waveguide systems. To address this, metasurface-based solutions are investigated. Metallic wire gratings based on Al act as polarisation filters with high extinction ratios and broad angular performance. TiO2 nanopillar metalenses are designed for beam collimation to suppress Lambertian emission and for beam steering to achieve precise angular control without bulky optics. Multi-layer configurations integrating polarisation, collimation, and beam steering are analysed, with the polariser–collimator–deviator stack providing the best performance in terms of efficiency and compatibility. A single metasurface combining polarisation filtering and collimation is also explored, offering a compact alternative despite lower transmittance. This work presents a systematic approach for achieving polarised, collimated, and steerable emission, enabling reduced optical path length and thinner, lighter, brighter, and more energy-efficient AR/VR light engines.