Electro- and photoswitching of undulation structures in planar cholesteric layers aligned by a polyimide film possessing various values of the anchoring energy

TL;DR

This study investigates how UV exposure and anchoring energy influence electro- and photoswitching of undulation structures in planar cholesteric liquid crystal layers, revealing controllable transitions and grating properties.

Contribution

It demonstrates the ability to switch undulation types in cholesteric layers via UV exposure and anchoring energy adjustments, advancing control over liquid crystal surface structures.

Findings

Different undulation types can be switched by UV exposure.

The period and diffraction efficiency of gratings depend on anchoring energy.

Sequential transitions from 2D to 1D undulation structures were achieved.

Abstract

The base for this manuscript was laid down by the studies carried out in the article by Senyuk B, et. al. Proceedings of SPIE. 2005; 5936: 59360W-1-9. In the present manuscript, a planar layer of the photosensitive cholesteric, based on the chiral dopant 2-(4'-phenylbenzylidene)-p-menthane-3-one dissolved in the nematic E7, under the alternating electric field was explored. In particular, the influence of UV exposure and the value of the azimuthal anchoring energy on electro- and photoswitching of undulation instabilities was considered. Due to the decrease in a ratio between the LC cell thickness d and the cholesteric helical pitch P, different types of undulations, observed under the electrical field, were switched by UV exposure. The change in the ratio d/P was realized owing to the unwinding of the photosensitive cholesteric helix during UV exposure in the LC cell with a fixed thickness d. Sequential transitions of types of the undulations from 2D to two 1D structures (1D|| and 1D_) were achieved. The undulation structure 1D|| with a controlled period of a grating in electric field was examined. Dependencies of jumps of the period and the diffraction efficiency of a photosensitive cholesteric grating on the anchoring energy of alignment layers were analyzed.