Optical phase conjugation in aqueous rhodamine 6G solutions and in rhodamine 6G embedded in polyvinyl alcohol films

Studies on optical phase conjugation by degenerate four-wave mixing in aqueous rhodamine 6G solutions and in rhodamine 6G embedded in polyvinyl alcohol thin films are presented. The experiments were performed at 532 nm using picosecond pulses. Strong nonlinearities were observed in both media for three different polarization configurations of the incoming beams. The time dependence of the signals was also studied and was similar in both media. The decay kinetics in each case reflects the competition between two different processes: a fast one related to the relaxation of the anisotropic absorption and a slower one associated with the decay of the stable S1 state.