Picosecond and nanosecond third order nonlinear optical characterization of Cu and Ni phthalocyanines using Z-scan technique

Herein we present our results from the picosecond and nanosecond nonlinear optical studies of two novel phthalocyanines {[(SO3Na)4CuPc] and [(SO3Na)4NiPc]} using the Z-scan technique. Open aperture Z-scan data revealed that the picosecond nonlinear absorption was dominated by three-photon absorption while in the nanosecond domain reverse saturable absorption prevailed. Closed aperture data with nanosecond pulses indicated strong thermal, negative nonlinearity while picosecond excitation demonstrated positive nonlinearity. The nonlinearity in CuPc was higher than in NiPc in both the time domains. The nonlinear coefficients extracted from the fits to experimental data were large compared to some of the recently reported works on similar molecules.