Optical Nonlinearity and Phase Coherence in CdSe and CdSexS1−x

The magnitude of the optical nonlinearity and its phase coherence are investigated at low temperatures in single crystals of CdSe and CdSexS1−x, using picosecond time resolved degenerate four‐wave mixing. In the pure compound semiconductors, the optical nonlinearity as well as the dephasing is governed by free exciton and biexciton interactions. In the mixed crystals, excitons localized by the alloy disorder play the dominant role, giving rise to larger nonlinearities and longer dephasing times than in the pure compounds.