Polarization Properties of the Electrically Controlled Twist-Planar Liquid Crystal Di.raction Structure

Abstract

The properties of the designed anisotropic diffraction structures based on the spatially structured electrically-controlled liquid crystal elements have been studied. Such a di.raction 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 diffraction 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 effect) the amplitude-to-phase transformation of the di.raction structure takes place and its diffraction e.ciency becomes higher. The proposed theoretical model enables one to explain the relationship between di.raction characteristics of a di.raction element and applied voltage or polarization of light. A good agreement of theoretical and experimental results is demonstrated.