EFFECT OF DEPHASING ON EXCITON SUPERRADIANCE AND EXCITON CAVITY POLARITONS

Quantum-well exciton superradiance and exciton cavity polarization for mation both require a substantial spatial coherence area in order to b ecome the dominant exciton field interaction. In both interaction proc esses the quantum-well (in-plane) momentum is conserved. Momentum scat tering, which is due, e.g., to interaction with a phonon reservoir, qu ickly localizes an initially delocalized exciton and randomizes the ex citation momentum. We take a close look at how momentum scattering inf luences measurements of excitonic superradiance and of exciton cavity polariton splitting. An important conclusion is that, in general, meas urements of the emitted light do not correspond to the evolution of th e system as a whole. Therefore, e.g., the measured decay rates do not correspond to the true decay rate of the system. (C) 1996 Optical Soci ety of America.