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 chi(ijkl)((3 )) of new tetrathiafulvalene derivatives, using the degenerate four-wave mi xing (DFWM) method. To understand the physical nature of the optical nonlin earities, we separate their electronic and nuclear contributions. The elect ronic contribution to the third-order nonlinear optical susceptibilities of the molecules turns out to be dominant. From DFWM measurements we also ded uce the values of the second-order hyperpolarizabilities gamma, which are s imilar to 10(5) greater than the gamma value of CS2 (C) 1998 Optical Societ y of America.