QUANTUM-ELECTRODYNAMIC EFFECTS IN SEMICONDUCTOR MICROCAVITIES - MICROLASERS AND COHERENT EXCITON-POLARITON EMISSION

We discuss the spontaneous emission of quantum well excitons in a mono lithic microcavity. When the quantum well is excited by a nonresonant pump wave at high above the bandgap, the incoherent spontaneous emissi on is concentrated on the single resonant mode and the laser threshold is reduced by many orders of magnitude. When the quantum well exciton is excited by a resonant pump wave, the coherent spontaneous emission based on a ''microcavity exciton-polariton'' is observed. The spectra l linewidth and the polarization of the pump wave are preserved and th e coupling efficiency into the single resonant mode approaches 100%. T he microcavity-induced normal mode splitting is observed in the freque ncy domain by photoexcitation spectrum measurements and in the time do main by pump-probe measurements.