Polarization instability in a polariton system in semiconductor microcavities

The kinetics of a field on a quantum well in the active region of a planar microcavity with strong exciton– photon coupling has been investigated under the conditions of resonance pulse excitation by a small degree of circular polarization. It has been shown that the system of polaritons at the early stage of the development of instability induced by polariton–polariton interaction tends to transit to a circularly polarized state, but does not reach $100$% circular polarization and returns to a polarized state whose polarization is close to the pump polarization. It has been shown that the observed effects are caused by the excitation of an unpolarized reservoir of excitons in quantum wells, which leads to fast relaxation of the difference between the effective resonance frequencies of excitons with different circular polarizations.