ACCELERATED RESPONSE OF PHOTOCHROMIC LIQUID-CRYSTALLINE CELL BY LASER-PULSE EXCITATION

Alignment relaxation of a photoresponsive liquid crystalline (LC) cell, in which a nematic phase is sandwiched between a pair of azobenzene (Az)-modified quartz plates, was measured by means of laser pulse excitation. The relaxation constant tau of the alignment change from the perpendicular state to the parallel state along the photoisomerization of Az showed wide variation between 1000 ms and 10 ms depending on the number of injected pulses and their intensity. The dependence of tau below 20 mJ/cm(2) excitation was consistent with the change in the photoisomerization yield of Az. Above this power, tau still showed moderate reduction although the photoisomerization yield approached a saturated value, indicating the presence of a secondary factor.