The threshold behavior of the stimulated parametric emission of dressed excitons in a microcavity is studied. The inelastic-phonon-scattering rates of the dressed exciton are calculated and are shown to be smaller than the bare quantum-well exciton values. The results describe the recently observed thresholdless photoemission behavior and predict a large stability for the dressed exciton modes inside a quantum-well microcavity.

• Received 15 November 1994

DOI:https://doi.org/10.1103/PhysRevB.51.7090