Light tuning of selective Bragg diffraction of the oblique helicoidal cholesteric

TL;DR

This paper investigates how AC electric fields and UV light influence the selective Bragg reflection in oblique helicoidal cholesteric structures formed in chiral nematic liquid crystals, revealing two distinct states under different electrical conditions.

Contribution

It introduces a method to tune Bragg diffraction in cholesteric liquid crystals using electric fields and UV light, highlighting the effects on the oblique helicoidal structure.

Findings

Ch$_{OH}$ structure exhibits two sequential states during Bragg reflection tuning.

Electric field frequency affects the Bragg reflection properties.

UV irradiation influences the cholesteric structure and its optical response.

Abstract

It is known that the oblique helicoidal cholesteric structure (Ch$_{OH}$), which is formed in alternating electrical field applied to the chiral nematic phase (N*) at temperatures above the chiral twist-bend nematic phase (N*$_{tb}$), can show selective Bragg reflection in the visible range of spectrum. In this work, we study the effects of AC electric field at different frequencies, as well as UV irradiation on the Bragg reflection of Ch$_{OH}$ structure of the N*$_{tb}$-forming mixture containing a light sensitive chiral azo-compound. It has been found that Ch$_{OH}$ structure shows two sequential states in the tuning of selective Bragg reflection at high and low electrical fields.