Abstract
The cholesteric liquid crystal (CLC) forms the periodic helical structure by its molecular chirality. This 1D photonic structure exhibits the Bragg reflection with characteristic polarization properties called selective reflection. In the present study, it has been shown that a helical pitch of the CLC could be reversibly controlled by the wavelength of the laser beam. The CLCs used were the mixtures of cholesterol derivatives doped with azobenzene. The variations of selective reflection band and the response time have been measured. It was confirmed that the helix of the CLC changed in the direction which intensified the inherent twisting power of the CLC by ultraviolet irradiation, and this change was analyzed in terms of the molecular statistical theory of Goossens.
