Bunching visibility of optical parametric emission in a semiconductor microcavity

The statistic of parametric photon emission in a one-dimensional semiconductor microcavity optical parametric oscillator is reported. We perform photon-counting experiments on signal and idler beams by means of a Hanbury Brown and Twiss setup for studying the second-order coherence. Under pulsed laser excitation at normal incidence, energy-degenerate signal and idler beams are emitted in a mirror-symmetric configuration and share the same excitonic/photonic composition. Moreover the two emissions share the same intensity and the same coherence properties. We show that the bunching visibility [i.e., the value of g ⁽2 ⁾(τ=0)] changes across the parametric threshold and it is associated both to different spectral composition of the emission and to the buildup of coherence at high injection. Nevertheless, different from conventional optical parametric oscillators, a full coherence is never recovered.