THEORY OF TIME-RESOLVED LIGHT-EMISSION FROM POLARITONS IN A SEMICONDUCTOR MICROCAVITY UNDER RESONANT EXCITATION

We develop a quantum mechanical model for the interaction of excitons in a microcavity embedded quantum well with a short resonant laser pul se. The model assumes full in-plane coherence. A Gaussian distribution of exciton slates is included in order to take into account the excit on inhomogeneous broadening. A coupling with a classical electromagnet ic held provides the initial excitation pulse, and the time dependent emitted signal is calculated. Very good agreement with the recent resu lts of time-resolved light emission under femtosecond resonant excitat ion by Norris et al. is obtained. We show that, in the strong coupling regime, the Rabi oscillations provide an energy transfer mechanism be tween the inhomogeneously broadened exciton levels, not present in the weak coupling regime or in the case of bare quantum;wells, which expl ains the very fast decay time of the measured signal. This mechanism i s considerably faster than the scattering of excitons due to interface roughness. Consequently, the in-plane wave vector is conserved in the polariton dynamics.