Defects of VK and Pb+ center type were created in Pb-doped samples by 4.03eV XeCl laser irradiation at 10K. Following irradiation, self-trapped and localized exciton emissions excited by the same XeCl laser line were observed as a result of the recombination of electrons, optically released from Pb+, with VK centers. A highly super-linear dependence of the emission intensity upon excitation intensity was found for the 3.65eV emission of the self-trapped exciton. A much weaker super-linearity was observed in the case of the visible localized exciton emission. Optical amplification of the exciton emission was suggested to be the most likely reason. An optical gain of 3.74 was calculated for the self-trapped exciton emission at 10K.

Stimulated Self-Trapped Exciton Emission in CsI:Pb. P.Fabeni, A.Krasnikov, M.Nikl, G.P.Pazzi, S.Zazubovich: Solid State Communications, 2003, 126[12], 665-9