Acoustic-phonon-mediated polariton photoluminescence in a GaAs bulk microcavity

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Abstract
Polariton photoluminescence from a GaAs bulk microcavity is investigated. Buildup of polariton emission is reported at zero detuning between strongly coupled bulk exciton and cavity photon modes. The buildup appears as a remarkable increase of optical emission from the lower cavity-polariton mode (LP) as a function of incident intensity and occurs before the bleaching condition is reached. At negative detunings, saturation of the LP emission takes place with the same increase of incident intensity, thus signaling a transition to the weak-coupling regime. In addition, the emission pattern after high excitation intensity becomes asymmetric at close to zero detunings where the ratio between LP and upper-polariton emissions is a factor of 4. Resonant luminescence spectra highlight the role of scattering with acoustic phonons during the relaxation mechanism and clarify the impact of localized excitons and exciton center-of-mass quantized states on the explanation of the experimental results.