Emission dynamics of a GaAs microcavity with embedded quantum wells under intense nonresonant excitation

In a GaAs-based microcavity with embedded quantum wells, the dynamics of emission processes under high levels of nonresonant picosecond laser-pulse excitation is studied. For pump levels above the stimulation threshold, the kinetics of the intensity, spectral position, and linewidth of the emission are measured. Upon the arrival of an excitation pulse, the emission line shifts to higher energies over a time interval comparable to the time it takes for the emission intensity to attain its peak value, and then shifts in the opposite direction towards its position at low polariton densities. The width of the emission line is largest immediately after the excitation pulse and attains a minimum when the stimulated-emission intensity is maximum. It is shown that after the excitation pulse, the system is initially in a weak exciton-photon coupling regime, and a transition to a strong-coupling regime occurs with time.