# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1706.04149