Parametric polariton amplification in semiconductor microcavities -: art. no. 127403

We present novel experimental results demonstrating the coherence properties of the nonlinear emission from semiconductor microcavities in the strong coupling regime, recently interpreted. by parametric polariton four-wave mixing. We use a geometry corresponding to degenerate four-wave mixing. In addition to the predicted threshold dependence of the emission on the pump power and spectral blueshift, we observe a phase dependence of the amplification which is a signature of a coherent polariton wave mixing process.