Polarization Properties of the Electrically Controlled Twist-Planar Liquid Crystal Difraction Structure

Abstract

The properties of the designed anisotropic difraction structures based on the spatially structured electrically-controlled liquid crystal elements have been studied. Such a difraction structure represents interchanging layers of a nematic liquid crystal with planar and twist orientations of the director. It is formed when a photosensitive polymer is subjected to the e ect of polarized ultraviolet radiation through a photolithographic mask. It is shown that increase in voltages leads to transformations of the liquid crystal structure. At minor voltages the difraction structure may be considered as two amplitude gratings with orthogonal polarizations at the output. At the voltage associated with the broken Mauguin condition (optical threshold of the twist efect) the amplitude-to-phase transformation of the difraction structure takes place and its difraction efciency becomes higher. The proposed theoretical model enables one to explain the relationship between difraction characteristics of a difraction element and applied voltage or polarization of light. A good agreement of theoretical and experimental results is demonstrated.