Self-Aggregation Enhanced Third-Order Optical Nonlinearities of Aryloxy Substituted Zinc Phthalocyanines

Third-order optical nonlinearities of three aryloxy substituted phthalocyanines are measured by femtosecond forward degenerate four-wave mixing technique at 800 nm. Ultrafast optical responses are observed and the magnitude of the second-order hyperpolarizabilities γ of the phthalocyanines is measured to be as large as 10^?31 esu. Due to the enhancement of J-aggregates, the γ value of an aryloxy substituted zinc phthalocyanine in chloroform is approximately 2.2 times larger than that of the dye in methanol. Moreover, the morphologies of aryloxy substituted zinc phthalocyanine in chloroform exhibit that the nanowires with a diameter of 50–100 nm are connected to each other to form an indefinite network structure, while no aggregates are detected when the samples are prepared from a solution in the methanol.