Dynamics of the cavity polariton in CdTe-based semiconductor microcavities:: Evidence for a relaxation edge

We present an experimental study of the photoluminescence dynamics of cavity polaritons in the low excitation regime, on a picosecond scale, as a function of the photon-exciton detuning. Time-integrated photoluminescence measurements in k space give direct evidence for the existence of a large nonequilibrium polariton distribution peaked at the crossing point of the cavity photon and exciton dispersion curves, when the detuning is negative. The relaxation-time k dependence explains the kinetic origin of this peak, showing the existence of a k-space relaxation edge, the so-called bottleneck.