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E. P. Pozhidaev^1,2, V. A. Barbashov^1,2, V. V. Kesaev¹, V. I. Pogonin³, S. A. Samagin¹, S. P. Kotova¹, S. I. Torgova¹, V. G. Chigrinov⁴

Author affiliations
¹P. N. Lebedev Physical Institute of RAS,
53 Leninsky Pr., Moscow, 119991, Russia
E-mail: epozhidaev@mail.ru
²Moscow Technological University (MIREA),
20 Stromynka St., Moscow, 107996, Russia
³Vernadsky Institute of Geochemistry and Analytical Chemistry of RAS,
19 Kosygin St., Moscow, 117975, Russia
⁴Hong Kong University of Science and Technology,
Clear Water Bay, Kowloon, Hong Kong

Abstract
We study experimentally electro-optical modulation in a planar aligned deformed-helix ferroelectric liquid crystal (DHFLC) with subwavelength helix pitch that is less than 100 nm, while thickness of the liquid crystal layer is around 50 μm. The electrically tunable phase shift of light from 0 to 2π and the ellipticity of the transmitted light were measured at the electro-optical response frequency of more than 1 kHz as functions of time and voltage applied across the cell. It is shown experimentally that under the conditions indicated above, the modulation of the ellipticity attenuates with decreasing wavelength of the incident light. It has been shown theoretically that even the maximum modulation of the ellipticity observed in experiments does not have a significant effect on the formation of light fields with nonzero angular momentum. Therefore, the planar aligned DHFLC cells with a thick liquid crystal layer can be used in those areas of optics where the pure phase modulation of light is required at frequency of more than 1 kHz.

Keywords: ferroelectric liquid crystals, phase shift of light, ellipticity, subwavelength helix pitch