RAPID OPTICAL SWITCHING BY MEANS OF PHOTOINDUCED CHANGE IN REFRACTIVE-INDEX OF AZOBENZENE LIQUID-CRYSTALS DETECTED BY REFLECTION-MODE ANALYSIS

Optical switching behavior of low-molecular-weight and polymer azobenz ene liquid crystals (LCs) was explored by means of reflection-mode ana lysis. Reflectivity changed on pulse irradiation under various conditi ons of orientations of LC molecules with respect to incident probe lig ht, either s-polarization or p-polarization. For the low-molecular-wei ght LCs, we obtained a response time of 100 mu s, which was very simil ar to that observed in the transmission-mode analysis, while we observ ed a decay time of 1 ms, which was significantly shorter than that obs erved in the transmission-mode analysis. The fast decay may be due to diffusion and reorientation processes which are characteristic of the reflection-mode analysis. For the polymer LCs, we observed a much slow er decay than those for the low-molecular-weight LCs.