Polariton parametric amplifier coherent dynamics

The polariton coherent dynamics in the parametric amplification regime is studied experimentally in a II–VI semiconductor microcavity, using angle-resolved four-wave mixing. We observe a strong reduction of the pump polarization dephasing time under excitation at the magic angle above the parametric amplification threshold. Our observations are analyzed by calculating numerically the coupled rate equations for the signal, pump and idler polariton fields. This allows us to interpret our observations in terms of time-dependent pump depletion. We find that the coherent dynamics above the threshold is the result of a complex interplay between parametric amplification and collision broadening.