New nonlinear features in the reflectivity and emission of microcavity polaritons

Summary form only given. In semiconductor microcavities, the strong coupling regime gives rise to mixed exciton-photon states named microcavity polaritons. For very low carrier densities, polaritons (like excitons) are expected to obey Bose statistics and may give rise to stimulated mechanisms. However, for large carrier densities, the fermionic nature of the exciton constituents dominates and leads to broadening of the polariton mode and reduction of the exciton oscillator strength. We report here on two beam experiments giving a closer insight into the nonlinear feature. The pump beam is non-resonant and modulated at low frequency while the probe beam is tuned across the lower polariton resonance.