Ultrafast coherent all-optical switching in quantum-well semiconductor microcavity

Picosecond degenerate four-wave mixing experiments at room temperature in a GaInAs-GaInAsP multiple quantum well embedded in a microcavity are presented. An input diffraction efficiency of 2% with only 1 mu J/cm(2) pump fluence is achieved. The authors show that the diffraction phenomenon is ultrafast and coherent. For a photon energy 30meV below the exciton band edge and for low pump intensities (1 mu J/cm(2)), the diffraction phenomenon is not perturbed by strong and spatially uniform pump pulse pre-illumination. This result demonstrates the potential of semiconductor microcavities for the realisation of ultrafast, sensitive and coherent devices.