Abstract
We report the stimulated-emission characteristics of CuI thin films with a thickness of 400 v nm grown on a (001) NaCl substrate by vacuum deposition. The energies of the heavy-hole and light-hole excitons in the CuI thin films are split at 10 v K by a thermal strain effect. Under intense excitation conditions, we have observed two types of photoluminescence bands originating from inelastic scattering of two n =1 heavy-hole excitons. One type is due to scattering into the n =2 heavy-hole-exciton state, and the other is due to scattering into the n =1 light-hole-exciton state. Optical gain spectra around the energies of these photoluminescence bands have been obtained by pump-probe measurements of transmittance. We discuss the excitation-power dependence of the optical gain based on a model for stimulated emission due to exciton-exciton scattering processes.