Time-resolved studies of stimulated emission from colloidal dye solutions.

The temporal profiles of the emission from titania particle suspensions in Rhodamine 640 perchlorate dye solutions excited by 10-ps pulses of 527-nm radiation were measured over a wide range of particle and dye concentrations and laser powers. The dynamics of stimulated emission from random media is modeled by a random walk of photons within the colloid and rate equations for molecular excitations. The pulse width and the dependence of the threshold for laser action on dye and scatter concentration are computed by a Monte Carlo simulation of the model and are found to be in qualitative agreement with experiment.