Determination of the molecular tilt profile of a liquid crystal under applied electric field by generalized transmission ellipsometry

Abstract

It has been demonstrated that, with the use of a standard rotating analyzer ellipsometer, generalized transmission ellipsometry (GTE) is able to uniquely determine the molecular tilt profile of a commercial nematic liquid crystal variable retarder (LCVR) with applied voltage. Also, the presence of the tilted anisotropic layer permits us to determine, solely with GTE measurements, both the ordinary and extraordinary indices of refraction of the liquid crystal. The isotropic layers of the LCVR, which are of no interest in this kind of measurement, can be completely omitted during modeling. The sensitivities of the technique to the determination of the ordinary index of refraction, the difference between ordinary and extraordinary indices of refraction, and tilt profile are discussed with strategies to improve the three. Previous measurements using guided modes that require special LCVR cells, or the complete modelling of the device due to the use of transmission and reflection data, are in agreement with the results obtained in this paper.