The Influence of Cell Thickness and Driving Voltage Shape on the Frequency Dispersions of Dielectric Characteristics of Ferrielectric Liquid Crystal

Abstract
Broad temperature range ferrielectric liquid crystal mixture FerriLCM-1 was previously developed by us in 2022 [Opt. Lett., 47, 1598, (2022)]. In this paper, we studied the frequency dependence of dielectric susceptibility of this mixture, as well as two critical electrical fields that characterize the ferrielectric phase. Liquid crystal cells of different thickness (1.85, 8.2, 11.4 and 57 µm) were examined at room temperature (23 °С). An increase in dielectric susceptibility was observed with an increase of cell thickness, while the value of the first critical electrical field decreased. It was shown that when the frequency and cell thickness increase, it become impossible to determine the value of the second critical electric field based on the field dependence on dielectric susceptibility. It was also shown for four different waveforms of applied voltage (alternating with an interval between pulses, rectangular, triangular, and sinusoidal) that there is practically no effect on the value of dielectric susceptibility. However, there is a noticeable effect on the frequency dispersion. These results are significant for the practical use of electro-optic phase modulators based on liquid crystalline ferrielectrics.

Keywords: ferrielectric liquid crystal, dielectric dispersion, dielectric susceptibility, various waveforms