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

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