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 ${\mathit{I}}_{\mathrm{sat}}^{\mathrm{incident}}$=100 W ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ leads to a saturation density ${\mathit{N}}_{\mathrm{sat}}^{100\phantom{\rule{0ex}{0ex}}\mathrm{K}}$=4.3\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ in good agreement with a theoretical model. These results are important for applications such as lasers in the strong-coupling regime and nonlinear devices.