Rotation of the plane of polarization of light in a semiconductor microcavity

We observe rotation of the plane of polarization of light in a microcavity parametric oscillator. The angle between the signal and pump polarizations ranges from 60 degrees to 120 degrees and depends strongly on the orientation of the pump polarization. Conversion of linear to circular polarization is detected for certain orientations of the pump polarization and shows a strong correlation with the rotation of the linear polarization. These effects are quantitatively described by a quantum model, which takes into account polariton-polariton scattering, longitudinal-transverse splitting, and self-induced Larmor precession. Evidence for an in-plane field oriented away from the main optical axes is found.