Optimization of the phase-modulation response of a TNLCD by means of a method based on Poincare sphere

摘要

In this contribution we describe a method for achieving a phase-only modulation regime with an off-the-shelf twisted nematic liquid crystal display (TNLCD). The keystone of this procedure involves illumination of an addressed TNLCD with circularly polarized light. The analysis of the distribution of the output polarization states in the S1-S2 plane as the applied voltage is changed suggests a simple way to optimize the liquid crystal phase response. For this purpose, a properly oriented quarter-wave plate followed by an analyzer is used behind the TNLCD. Laboratory results for a commercial display are presented. Our experiments show a phase modulation depth of 240o for a wavelength of 514 nm with a residual intensity variation lower than 4%.