2C07 Mechanism and response characteristics of helical pitch changes by photoisomerization of azobenzene

Abstract

A helical pitch in cholesteric liquid crystals doped with azobenzene changes by ultraviolet and visible light irradiation. Using this phenomenon, we have demonstrated the optical switching and the image recording. However, the response time of hundred seconds was not enough for optical applications. To improve response speed, the relation between isomerization of AB and pitch change was investigated by real-time absorption spectroscopy during laser irradiation. We found that the response time consisted of three process times: dye isomerization, pitch elongation and pitch reformation. Isomerization process was enough fast, whereas successive processes were quite slow. By optimization of experimental conditions, response time was shortened to the order of a second.