Picosecond spectroscopic studies of spontaneous and stimulated emission in organic dye molecules

Abstract

Stimulated emission from organic dyes provides us with the potential for producing tunable, short pulsed lasers. Stimulated emission can also interfere in the measurement of excited state lifetimes of dyes when excited by intense picosecond pulses. Time-resolved measurements of the emission from several organic dyes as a function of excitation intensity have been carried out in order to determine the conditions for obtaining efficient dye lasers and correct excited state lifetimes. A long build-up time for the stimulated emission (≈) 60 ps for a 6–8 ps exciting pulse) has been observed and confirmed by a theoretical model. Calculations using this model show that, even in the presence of very weak stimulated emission, the emission intensity does not decay in the same manner as the density of excited molecules.