Evidence of polariton stimulation in semiconductor microcavities

Stimulated photoluminescence of the lower polariton in CdTe microcavities is studied at low temperature, using nonresonant excitation. The stimulation threshold is found to be independent of the number of quantum wells in the microcavities, which rules out the stimulation model based on population inversion of either localized excitons or electron-hole plasma. On the other hand, the bosonic final state stimulation process, or boser effect, is clearly evidenced by tuning the lower polariton to one LO phonon below the exciton reservoir. For detunings closer to zero, the stimulation is dominated by another physical mechanism, that could be the exciton-exciton scattering into the upper and lower polariton states.