Parametric scattering in semiconductor microcavities probed by four-wave mixing

We present a study of the polariton coherent dynamics in II-VI semiconductor microcavities in the parametric scattering regime. We perform angle resolved four-wave mixing, which allows us to study the polariton dephasing within the full reciprocal space. When polaritons are excited above the threshold in the phase matching conditions for parametric scattering, we observe a very efficient scattering towards the final states (signal and idler), inducing pump depletion. On the contrary, below threshold or when the phase matching conditions are not fulfilled, we observe an angle-dependent collision broadening that occurs when pump polaritons scatter towards the excitonic reservoir. We discuss the interplay between parametric scattering and collision broadening within the framework of a phenomenological numeric calculation. Last, we propose a new design for the realization of a vertical-cavity, surface emitting parametric oscillator/amplifier that provides triple resonance for the parametric frequencies together with cavity phase-matching for all waves at normal incidence.