Low excitation photoluminescence dynamics of polaritons in II-VI microcavities

We have investigated the photoluminescence (PL) dynamics of microcavity pol aritons for non-resonant. low-power excitation as a function of the photon- exciton detuning on a picosecond time scale at 9 K. For negative detuning w e give clear experimental evidence for the appearance of a slow-down of the relaxation processes inhibiting total thermalisation of the polariton popu lation. This can be well explained by the inefficiency of the coupling betw een acoustic phonons and photon-like polaritons. Furthermore, we will discu ss separately both the influence of the effective oscillator strength and o f the dark excitonic states on the PL dynamics by varying the number of qua ntum wells.