Saturation of the strong-coupling regime in a semiconductor microcavity: Free-carrier bleaching of cavity polaritons

We present experimental data on saturation of the strong-coupling regime in semiconductor microcavities based on intensity-dependent photoluminescence measurements. The saturation can be understood in terms of electron-hole pair screening of the quantum-well exciton. The very low saturation intensity Isatincident=100 W cm-2 leads to a saturation density Nsat100K=4.3×1010 cm-2 in good agreement with a theoretical model. These results are important for applications such as lasers in the strong-coupling regime and nonlinear devices.