Analysis of the possibilities to generate and analyze different polarization states of light by twisted nematic liquid crystal

Abstract

Twisted nematic liquid crystals (TNLCs) are an interesting alternative to the linear liquid crystal variable retarders commonly used in polarimetric systems. The first and last molecules are anchored on the bounding surface of the liquid crystal cell at 90° angles to each other. As a result of the application of an electric field, there is a change in the polarization properties of the eigenvectors of the TNLC and the phase difference introduced by them. Theoretical analysis indicates that the use of TNLC can generate and analyze an infinite number of polarization states. Nevertheless, their practical applicability is limited and depends on the physical parameters of the liquid crystal cell. Therefore, this work presents the polarimetric characteristics (azimuth angle, ellipticity angle and phase difference) measured as a function of applied voltage of two TNLCs manufactured by Thorlabs®. The study aims to test whether it is possible to achieve a phase difference greater than 4π by using TNLC, which is desirable for optimization reasons. The polarization states that can be produced and analyzed with the examined TNLCs are represented on the Poincaré sphere. This provides a base for selecting the optimal practically possible polariscope configurations in the future.