Nonlinear dynamics of liquid crystal: ultrasonic light modulator

Abstract

Abstract The article discusses the influence on the physical properties of a planar-oriented cholesteric liquid crystal (chlesterylpelargonate) with a thickness of 10-15 microns, the propagation of elastic waves in the ultrasonic range (exposure frequency 600 kHz). Changing the pitch of the crystal spiral leads to changes in its optical properties, which is shown in the modulation spectrum of light reflection from the cholesteric layer in the selective scattering region. It was found that a positive peak is observed at a light wavelength of 436 nm, and a negative peak at 427 nm. A technique of experimental measurements is proposed, which uses the principles of modulation spectroscopy, which makes it possible to record with a high degree of accuracy even insignificant changes in optical spectra, which are not possible to register with conventional optical spectrometers. By analyzing the reconstructed reflection spectrum, it can be concluded how the swirling of a liquid crystal affects the processes that occur in it during the propagation of ultrasonic waves. The considered nonlinear processes are interesting for creating ultrasonic light modulators based on liquid crystals.