Relaxation kinetics for temperature and degeneracy of microcavity polaritons

We apply a semi-classical Boltzmann kinetics for a gas of laser-pulse excited microcavity polaritons taking into account their mutual interaction and their interaction with acoustic phonons. Fitting the temporally evolving polariton distribution above the ground state with a Bose–Einstein distribution, we find the evolution of the temperature and the degeneracy parameter, i.e. the ratio of the chemical potential to the thermal energy. Studying the relaxation in particular for GaAs microcavities we compare our results with recent measurements by Deng et al. In agreement with the experiment we find that the lattice temperature can be reached and that the degeneracy of the condensed gas holds up to 60–80 ps provided a detuning of the cavity mode is applied which increases the exciton component of the lower-branch polaritons and thus their scattering rates.