Impact of exciton localization on cavity polaritons

Polariton emission was investigated in a GaAs-based microcavity (MC) under various excitation conditions which excite predominately hot excitons and carriers, localized excitons, or a mixed system. Strong differences have been found both in the intensity, the energy distribution, and the temperature dependence of the lower branch polariton (LP) emission for the different excitation conditions. In MCs with negative detuning, LP states are filled via relaxation of mobile excitons delocalized due to either thermal activation or interaction with hot carriers. In MCs with positive detuning, in contrast, the energy relaxation of photoexcited LPs is more effective whereas an additional above-band-gap excitation leads to a strong decrease of population at the LP band bottom.