Excitonic origin of femtosecond nonlinearity near the bandgap of a commercial CdSSe semiconductor-doped glass

Abstract

To determine the origin of the nonlinearity near the bandgap of II-VI commercial semiconductor-doped glasses (SDG) with no apparent excitonic features, we studied the temperature dependence of the dephasing time near the bandgap using degenerate four-wave mixing (FWM). The deduced coupling constant with LO phonons was comparable, or nearly equal, to the exciton-LO phonon coupling constants in other II-VI semiconductors and quantum wells. We contend that the nonlinearity observed in FWM is due to excitons, whose features in absorption are overshadowed by the inhomogeneity in the crystal sizes.