Transient spectroscopy of near-condensate modes in the system of exciton polaritons in a semiconductor microcavity

A transient spectroscopy technique for studying near-condensate modes of exciton polaritons in high-quality-factor planar semiconductor microcavities is proposed. It is demonstrated that, under the conditions of coherent external pumping, the transition to the upper steady state of an optically bistable condensate is accompanied by the excitation of near-condensate modes. They manifest themselves in the appearance of transient oscillations of the polariton intensity as the system switches to the upper branch of the S-shaped bistable pump dependence of the intensity. Analysis of the time-resolved spectra of these oscillations provides information on interactions in the system and the evolution of the exciton-polariton condensate density.