Color-selective geometric phase lens for apochromatic lens system

Abstract

Thin lenses have potentially much lower weight and volume than traditional refractive lenses, and therefore enable compelling solutions in augmented-/virtual-/mixed-reality (AR/VR/MR) headsets. The geometric-phase lens (GPL), formed either with liquid crystals (LCs) or metasurfaces, is emerging as a leading technology because of its ability to implement arbitrary aspherical phase profiles and its potential for low loss and minimal ghosting. However, a strong chromatic dispersion is inherent to each singlet. One prior method to overcome this employs a stack of multiple achromatic GPLs acting on all colors simultaneously with color filters and other waveplates to achieve an apochromatic lens system. Another concept in the prior art is to use multiple color-selective GPLs (CS-GPLs) wherein each diffracts only a single color while transmitting the others. In this work, we report on a family of color-selective GPLs with highly chromatic efficiency spectra, made using multi-twist LC coatings. In both theory and experiment, we show the diffraction efficiency of red, green, and blue lenses is high (< 91%) while the complementary colors of each coating are almost fully transmitted undiffracted. The CS-GPLs is a promising optical element to provide a new route to mitigate the chromatic abberation in the AR/VR/MR lens system.