Stimulated emission in high-gain organic media

Stimulated emission was studied in various scattering gain media, including thin p-conjugated polymer films, organic dyes-doped gel films, and opal crystals saturated with polymer and laser dye solutions. We found that at high excitation intensities a featureless amplified spontaneous emission band transforms into a finely structured spectrum having features as narrow as 0.1 nm. Stimulated emission in this regime is directional and characterized by a linear laserlike intensity dependence. We speculate that this phenomenon is due to optical feedback caused by light scattering inside the inhomogeneous gain media.