Application of the flexoelectric effect in liquid crystals to create acousto-optic transducers

Abstract

The flexoelectric effect in nematic liquid crystals was studied using acoustic modulation spectroscopy. A cell consisting of three plates separated by spacers was used. The movable plate made shear oscillations in the plane of the cell. We studied thin layers of liquid crystals with homeotropic orientation of molecules with a thickness of from 20 to 100 microns. The frequency of exposure is 1 kHz. In the framework of the de Gennes model, near the phase transition liquid crystal - isotropic phase, the resulting signal has a flexoelectric nature and is due to a dipole mechanism. In this work, the temperature dependences of the flexosignal, the temperature effect on the value of the average constant angle of inclination (θc) and the amplitude of the oscillations of the director (θd) of a liquid crystal are investigated. The dependences of flex coefficients e33 on temperature are obtained. It was found that dipole and quadrupole mechanisms contribute to the observed molecular orientational polarization. The results of this study are proposed to be used to create liquid crystal transparencies of the new generation, as well as acousto-optic transducers for automated vibration control systems, since the use of liquid crystals provides a number of advantages (lightweight construction, low power consumption and overall dimensions, low cost).