All-optical control of selective reflection of cholesteric liquid crystals (Ch-LCs) containing an azobenzene derivative as a photoresponsive chiral dopant was investigated. The photoresponsive Ch-LCs was comfirmed first to reflect selectively visible light in narrow wavelength range at room temperature. Photoisomerization of the azobenzene occurred in the Ch-LC phase upon irradiation with ultraviolet or visible light. The observed effect was revealed to be due to change in the selective reflection. Color change between two different reflective lights was reversibly controlled by alternating irradiation of ultraviolet and visible lights. The photoresponsiveness of the Ch-LCs depended on the chirality of an azobenzene molecule.
