The ultrafast processes of tetra-phenyl-porphyrin(TPP), tetra-t-butyl-phthalocyanine(BuPc) and nitro-tri-t-butyl-phthalocyanine (NtBuPc) have been inves-tigated using the femtosecond time-resolved fluorescence depletion method. A sharp peakof the fluorescence depletion with delay time has been observed both for TPP and BuPc.An ultrafast two-photon absorption process has been proposed to explain the sharp peakobserved. A long-lived fluorescence depletion has also been observed. It is causing by thestimulated-emission-pumping process produced by the intense probe laser pulses.
