Collective dynamics of excitons and polaritons in semiconductor nanostructures

Time-resolved photoluminescence is a powerful technique to study the collective dynamics of excitons and polaritons in semiconductor nanostructures. We present a two-pulse excitation technique to induce the ultrafast and controlled quenching of the exciton emission in a quantum well. The depth of the dip is given by the magnitude of the warming of the carriers induced by the arrival of a laser pulse when an exciton population is already present in the sample. We use this technique to study the relaxation mechanisms of polaritons in semiconductor microcavities, which are of great importance to enhance the conditions for their condensation under non-resonant excitation. We also explore the dynamics of polariton fluids resonantly created in the lower polariton branch in a triggered optical parametric oscillator configuration, showing the first evidence of polariton superfluidity, and opening up the way to the real-time study of quantum fluids. (tutorial)