Two-, three-, and four-photon-pumped stimulated emission (cavityless lasing) properties of ten novel stilbazolium dyes in solution phase have been comprehensively studied. These newly synthesized multiphoton active dye compounds have the same molecular backbone but differ either in their electron donors or in their electron acceptors and can be utilized to generate highly directional stimulated emissions over a broad visible spectral range (from 490 to 618 nm) under multiphoton-pump conditions. The pump source was a powerful Ti:sapphire oscillator-amplifier system associated with an optical-parametric generator, which could specifically provide similar to 160 fs duration and similar to 775, 1320, and 1890 nm laser pulses for two-, three-, and four-photon excitation, respectively. The spectral, spatial, and temporal properties as well as the efficiency of multiphoton-pumped lasing output from different dye-solution samples have been studied. Based on the measured results, two salient features have been found: (i) the threshold pump-energy values for two-, three-, and four-photon-pumped lasing were quite close (within a factor of 3-4); and (ii) there was an obvious wavelength difference (10-30 nm) between the forward and backward lasing output under three- and four-photon-pump conditions. (c) 2005 Optical Society of America.
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