Spectral measurements of the emission from highly scattering gain media

Abstract

The spectral properties of the emission of a colloidal suspension of titanium dioxide particles in Rhodamine 640 perchlorate were studied systematically. The particle density $\rho$, the dye concentration $c$, and the energy of the pump pulse were varied over several orders of magnitude; the dependence of the spectra on these three parameters is discussed. We discovered a strong correlation between the particle density and the dye concentration. The amplification by stimulated emission was found to be strongest when the absorption length $l_a$ and the mean-free-path length $l^{*}$ had approximately the same magnitude. The respective $l^{*}$ values were determined by a pulsed transmission experiment.