Experimental investigation of photoluminescence dynamics of cavity polaritons under nonresonant excitation

Low-temperature time-resolved photoluminescence (PL) experiments have been performed on a semiconductor planar microcavity, which contains two sets of three In0.13Ga0.87As/GaAs quantum wells embedded in a 3 lambda /2 GaAs cav ity. The spontaneous emission dynamics of both lower- and upper-branch pola ritons is investigated as a function of exciton-cavity detuning under nonre sonant optical excitation. It is found that the PL decay times of both bran ches are independent of cavity detuning while the PL rising kinetics of the lower- and upper-branch polaritons exhibits a significant difference. The rise time of the upper polarition branch shows a strong dependence on cavit y detuning, while the rise time of the lower polarition branch is less sens itive to cavity detuning. Our results can be well understood in the framewo rk of the theoretical prediction of Tassone et al.