Resonant Third-Order Optical Nonlinearities of Poly(methyl methacrylate) Films Containing J-Like Aggregates of a Thiadicarbocyanine Dye

The third-order optical nonlinearities and responses of poly(methyl methacrylate) (PMMA) coating films containing J-like aggregates of a thiadicarbocyanine dye, 3,3’-diethyl-2,2’-thiadicarbocyanine iodide (DTDCI), are measured by degenerate four-wave mixing (DFWM) technique under resonant conditions. The temporal profiles of the DFWM signal of PMMA coating films containing J-like aggregates of DTDCI are found to consist of three components: i.e., the coherent instantaneous nonlinear response (electronic response) and the two slow responses with decay time constants of about 0.8ps and about 7.0ps. The electronic component of the effective third-order nonlinear susceptibility, x⁽³⁾_e, of one of the present films is as high as about 2.1 × 10^-8esu, and the figure of merit of third-order nonlinearity F (F =x⁽³⁾/α) is evaluated to be about 1.9 × 10^-13esu cm at 850nm.