Stimulated emission and E-H plasma in gallium selenide

The stimulated emission from extremely high quality GaSe crystals is investigated at very high values of excitation intensity by means of a nitrogen laser. The rising of the laser action due to electron-hole plasma recombination is reported. The unsaturated optical gain spectrum confirms the stimulated effect either from excitonic interaction processes or from electron-hole plasma. The role of the surface quality of the samples in the competition among these two amplification mechanisms is particularly discussed.