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I. V. Simdyankin, A. R. Geivandov, M. I. Barnik, V. S. Palto, S. P. Palto

Author affiliations
Shubnikov Institute of Crystallography of Federal Scientific Research Centre «Crystallography and Photonics» of Russian Academy of Sciences,
59 Leninsky Prosp., Moscow, 19333, Russia
E-mail: ageivandov@yandex.ru

Abstract
The spectral characteristics of cholesteric liquid crystals (CLC) in a non-uniform pulsed electric field created using two systems of interdigitated electrodes are studied. The new data confirm the results obtained earlier for a uniform field and associated with the absence of continuous unwinding of the helix and the induction of intense higher-order selective reflection bands. The experimental data are in good agreement with the results of numerical simulation. The selective reflection bands induced by the electric field and their triple-zone structure are reproduced in the experiment.
The pulsed mode of application of the electric field allows you to create an electric field strength well above the critical value E_c, capable of full unwinding the CLC helix (in the approximation of the unlimited spiral according to de Gennes theory). At the same time, no signs of unwinding were found, which again indirectly confirms the fact that spinning a spiral in a limited geometry without the formation of defects is impossible.

Keywords: chiral liquid crystals, cholesterics, selective reflection, electrooptics