Photo-induced ultrafast process of third-order optical nonlinearity in bacteriorhodopsin

Photo-induced ultrafast process in bacteriorhodopsin was observed with DFWM technique. The origin of the fast component(ps) and the slow component (ns ) in photo-excitation dynamics was explained on the basis of models of both the phase space filling and the conformational deformation. The former is due to the excitons made from free electron-hole pairs and the latter is ow ing to the polaron induced from the non-radiative decay. The saturation den sity and length of excitons, the life time of exciton and polaron, and the polaron state formation efficiency were extracted by a least square fitting procedure.