Third-order optical nonlinearities of several naphthalocyanines and porphyrins measured by the resonant femtosecond DFWM technique

Abstract

We present the experimental results on the third-order nonlinearities of several porphyrin and naphthalocyanine derivatives measured by the femtosecond degenerate four-wave mixing (DFWM) technique under resonant conditions. Studies in the solvent effect on the third-order optical nonlinearities indicate that molecular packing in the solutions has significant effects both on the magnitude of the third-order nonlinear optical susceptibility, χ⁽³⁾, and the DFWM response. The electronic component of the molecular hyperpolarizability, γ_e, was evaluated to be in the range of 0.9 x 10^-29 esu to 2.3 x 10^-29 esu for these compounds, where the zinc complex of the porphyrin derivative (ZnTTMAPP) showed the largest γe. These values are two orders of magnitude larger than the reported values measured under non-resonant conditions. The time-resolved results indicate that the relaxation of the excited state population dominates the DFWM response in these macrocycles.