Reflective optical components based on chiral liquid crystal for head-up displays

The emerging near-eye displays for see-through augmented reality (AR) and virtual reality (VR) have inspired new applications of optical gratings, for example, as waveguide-coupling components. For such applications, reflective diffraction gratings and reflective lenses based on self-organised chiral liquid crystal (CLC) are strong contenders because of their high diffraction efficiency and unique polarisation selectivity. However, in order to design optical systems that use such components, the optical properties of CLC diffraction gratings need to be thoroughly investigated and understood. In order to better understand the structure and diffraction properties of such components we simulated the behaviour of two cholesteric liquid crystal configurations (planar and slanted) and compared them with experimental results. This paper covers advancements in CLC diffraction grating research, comparison between different theories for the director configuration in the bulk and further investigation of the optical properties of the devices. The evolution of reflective CLC lenses is discussed and lenses with a small f - number are described. In this review paper we show that progress made in the field of CLC-based flat optics has a high potential for AR/VR display systems.