Reflective Polarization Volume Lens with Small <i>f</i>‐Number and Large Diffraction Angle
Kun Yin, Ziqian He, Shin‐Tson Wu
Abstract
Abstract Planar optics based on patterned cholesteric liquid crystals (CLCs) has attracted increasing attention owing to the self‐organized helical structure and the ability to create arbitrary reflected wavefront through spatial orientation control. However, because of the subwavelength‐orientation requirement, it is challenging for liquid crystal lens to achieve a low f ‐number ( f /#) and large deflection angle simultaneously. Furthermore, with the increasing demand for compact size in novel optical systems, reflective lens has advantage over the transmissive one because it can fold the optical path. Here, a new off‐axis reflective polarization volume lens (PVL) with f /# = 0.825, large aperture size, simple fabrication process, thin profile, circular polarization selectivity, and large diffraction angle is proposed. In contrast to traditional vertical spiral structure, PVL is based on patterned CLCs with a slanted helical axis. In this paper, the PVL is theoretically evaluated and then three reflective PVLs at red, green, and blue wavelengths (R = 605 nm, G = 532 nm, and B = 450 nm) are fabricated. Meanwhile, a simple approach is utilized to achieve 20 mm diameter and 16.5 mm focal length. The low scattering and good image quality of reflective PVL enrich these functional devices and provide promising applications to novel foldable optical systems and waveguide‐based wearable near‐eye displays.