Bragg polarization gratings used as switchable elements in AR/VR holographic displays

The high coherence of laser light sources is a key to the application of diffractive optics usable in holographic AR/VR displays. This can be combined with switchable diffractive elements, which are advantageous for several optical functions used in immersive holographic displays such as shutters, polarization filters, for rapid beam deflection and selection. We demonstrate a compact, effective and robust diffraction wide-angle switchable beam-deflecting device based on circular polarization gratings possessing Bragg-performances (Bragg-PG) and a polarization switch. Such grating/polarization switch pair may, for instance, be a discrete switchable deflection element or as a switching element for pre-deflection with field lenses for application in holographic AR/VR displays. Micrometer-thick circular polarization gratings characterized by high diffraction efficiency (DE > 95%), large diffraction angles ( 95% in the vis spectral range) and stable symmetric and slanted circular Bragg polarization gratings were fabricated using the developed material and processing technique. The high usable diffraction angles combined with high DE make the Bragg-PG attractive for HMD AR/VR applications because of the system inherent short focus lengths and large numerical apertures needed to meet the low space budget in HMD and other optical systems.