Nonlinear optical responses of C70-toluene solutions

The third-order optical nonlinear response in C70-toluene solutions was studied by time-resolved degenerate four-wave mixing at 532 nm. Both the rise and decay time of the four-wave mixing signal were measured as a function of laser excitation energy. The observed decrease of the rise time as excitation intensity increases is attributed to the large singlet-singlet excited state absorption cross section. The decay time of the nonlinear response depended on the sample age and laser excitation and varied from 110 to 650 ps within the range of the various widely diverging published values.