Quantum coherent effects in cavity exciton polariton systems

The non-linear emission from semiconductor microcavities in the strong coupling regime exhibits specific coherence properties that can be interpreted by parametric polariton four-wave mixing. In a geometry corresponding to degenerate four-wave mixing, we predict and observe a phase dependence of the amplification which is a signature of a coherent polariton wave mixing process. This process is also expected to lead to bistability and squeezed light generation. Spatial effects in the non-linear regime are evidenced, and spatial filtering is required in order to optimize the measured squeezing which is observed close to the bistability turning point. Moreover, the presence of strong coupling inside the microcavity allows to produce a new type of squeezing involving a part-light, part-matter field, the polariton.