Electronic and nuclear contributions to the third-order nonlinear optical susceptibilities of new p-N, N'-dimethylaniline tetrathiafulvalene derivatives.

We report large third-order nonlinear optical susceptibilities (?3?)(ijkl) of new tetrathiafulvalene derivatives, using the degenerate four-wave mixing (DFWM) method. To understand the physical nature of the optical nonlinearities, we separate their electronic and nuclear contributions. The electronic contribution to the third-order nonlinear optical susceptibilities of the molecules turns out to be dominant. From DFWM measurements we also deduce the values of the second-order hyperpolarizabilities gamma, which are ~10(5) greater than the gamma value of CS(2).