Polaritonic polarization effects in a semiconductor microcavity

The polarisation properties of the emission from a semiconductor microcavity are studied in the stimulated parametric scattering regime, when excited by linearly polarised resonant excitation of the lower polariton branch. The emission of the signal at k=0 is found to exhibit significant degrees of linear and circular polarisation. This is accompanied by rotation of the plane of the linearly polarised light, relative to the pump state, in the range from 60° to 120°. In particular, when the signal emission is purely linearly polarised, the plane of the light is perpendicular to that of the pumping laser beam. These effects are explained taking into account the anisotropy of polariton–polariton scattering as well as the energy splittings between circular and linear polarised polariton states.