Abstract

In this paper we present the observation of the amplification of spontaneous emission from optically pumped animal tissues treated with fluorescent dyes. The temporal and spectral responses of the emission were measured as a function of pump intensity. This observation is attributed to the increase in optical gain in dye-stained tissue media. The scattering takes place from the structures inside and outside the 10μm-size of the cells. The large size of the cell causes the scattering to be mostly in the forward direction. The transport-scattering mean-free-path lengths l_tr in tissues such as fat and muscle and of the order of l_tr = 0.5 mm (fats) and l_tr= 3 mm (muscle). The lasing effect in a biological tissue could come form several factors, such as morphological resonance effects within the cells, localization, feedback from the longer path of scattering photons, and microcavity formation due to intercellular scatterings.

© 1995 Optical Society of America