Light-induced control of selective Bragg diffraction of the oblique helicoidal cholesteric

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