Polariton correlation in microcavities produced by parametric scattering

The spontaneous and self-stimulated parametric emission from a semiconductor microcavity after resonant pulsed excitation is measured. The emission of the lower polariton branch is resolved in two-dimensional momentum space, using either time-resolved or spectrally resolved detection. The polariton–polariton scattering dynamics is generally in good agreement with the theory using the nonlinearity due to the excitonic part and the dispersion due to the photonic part of the polariton. The peculiar figure-8 shaped distribution in momentum space of the final states of the parametric scattering is observed. Renormalization of the dispersion due to the bound biexciton state is found to influence the final state distribution. Using two pump directions the shape of the final state distribution can be changed to a peanut or oval for the mixed parametric processes. In this dual pump configuration, we find that polaritons in two distinct idler-modes interfere if and only if they share the same signal-mode, showing the existence of polariton pair correlations that store the “which-way” information