Many-body and correlation effects in semiconductor microcavities

We discuss the influence of many-body and correlation effects on the transient optical response of semiconductor microcavities. The complexity induced by the Coulomb interaction between electrons determines the non-instantaneous character of exciton-exciton collisions. We show that the exciton-photon coupling in semiconductor microcavities is able to alter the exciton dynamics during collisions strongly affecting the effective scattering rates. This influence determines the very different nonlinear absorption rates of the two polariton branches observed in many experiments. This analysis also clarifies the origin of the great enhancement of polariton parametric amplification observed when increasing the polariton splitting. It demonstrates that exciton-exciton collisions in semiconductor microcavities can be controlled and engineered to produce almost decoherence-free collisions for the realization of all-optical microscopic devices.