$^1$Belarusian State University. $^2$ Institute of Chemistry of New Materials of the National Academy of Sciences, Belarus

One of the promising areas in modern photonics is the use of a new principle for constructing electrically switchable liquid crystal (LC) diffraction elements based on the use of a spatially modulated geometric phase (the Pancharatnam–Berry phase) of a light wave, which makes it possible to achieve diffraction efficiency close to 100 %. In the work, a polarizing diffractive LC element with a twist director orientation was created and an experimental and theoretical analysis of its electrically controlled diffraction properties was carried out. It is shown that at a control electric voltage level of about 2.8 V, the LC layer undergoes separation into two independent anisotropic sublayers. One of which functions as a diffraction structure, and the second performs the functions of an optical phase plate. Thus, the diffractive LC element replaces several static devices in its functionality: a polarizer, a phase plate, a diffraction grating with the ability to electrically switch the period. The dependence of the element diffraction properties in relation to the side of circularly polarized radiation input, electrical switching of the diffraction structure period from $\Lambda_1$ = 20 $\mu$m to $\Lambda_2$ = 10 $\mu$m, achievement of a diffraction efficiency of 91 % at a control voltage of 2.8 V (LC layer thickness of 10 $\mu$m) and the simultaneous formation of two circularly polarized orthogonal coherent waves are demonstrated. The ability to electrically control the polarization-dependent diffraction properties of a device is promising for modern holographic technologies, quantum computing, information coding and processing, etc.