Laser action in condensed disordered media of active dye-stained animal tissues and sandy colloidal scattering walls.

Significant narrowing of both the spectral and temporal profiles of emission radiation from optically pumped dyes was observed in discrete and continuously disordered media such as dilute colloidal dye solutions and densely packed forms of sandy powders and animal tissue treated with rhodamine 640 dye solution. The narrowing of the spectral and temporal response is attributed to laser action arising from feedback of the emission radiation from the surrounding scattering walls into the photoexcited dye regions of the animal and sandy colloidal disordered media.