Signatures of exciton-cavity coupling in semiconductor microcavities

We have used photoluminescence measurements to investigate the dynamic coupling between excitons and cavity modes when a quantum well is embedded in a microcavity. The experiments were carried out in quantum wells placed at either the antinodes or the nodes of the optical field in a 3λ/2 cavity, in a broad temperature range (200-6 K) and using magnetic fields up to 7 T. We find that light is emitted by the exciton-cavity system before it has time to thermalize. The lack of thermalization is most dramatic at low temperature, where the luminescence spectrum shows two peaks of comparable strength separated by 6 meV, attributed to emission from the low- and high-energy branches of the coupled system.