Diffraction optical elements with nematic liquid crystals and their applications

In this paper consideration is being given to the principle underlying the operation of switchable diffraction elements based on the relief grating of isotropic material and nematic liquid crystals contacting it. Electrical control of the phase grating diffraction efficiency has been experimentally realised. The problems of LC orientation on the relief substrate have been considered. Consideration has also been given to the optical diffraction lens with switchable focal lengths and to two - layer systems operating with radiation of any polarisation. It has been demonstrated that LC having large value of optical anisotropy (similar to 0.2) are most suitable for this application. The requirements to liquid crystals to be used in optical elements are covered.