Using birefringence colors to evaluate a tunable liquid-crystal q-plate

摘要

Q-plates are geometrical phase elements that enable the realization of vector beams in simple and compact optical setups. In this work, we consider a tunable liquid-crystal commercial q-plate operative in the visible and near-IR range and study its spectral and color birefringence properties under broadband illumination. We first characterize the spectral retardance function of the device in a wide range from 400 to 1600 nm and determine how it changes upon applied voltage. Then we evaluate the color transmission characteristics when inserting the q-plate between crossed and parallel linear polarizers. These color properties agree with the trajectory in the CIExy chromaticity diagram as the applied voltage changes. Finally, we demonstrate that a simple visual inspection of the transmitted birefringence color perceived when placing the q-plate between crossed polarizers can be used to obtain a rapid estimation of the q-plate retardance at given wavelength ranges. (C) 2019 Optical Society of America