Photoluminescence excitation spectroscopy of semiconductor microcavities

Photoluminescence excitation (PLE) experiments in a Al_0.25Ga_0.75As microcavity, with GaAs quantum wells embedded in it, have revealed strong exciton-cavity coupling. By monitoring the low-temperature (T = 10 K) photoluminescence (PL) from the GaAs substrate on which the microcavity is grown, we have observed a double peak of the PL intensity as a function of excitation photon energy in the 1.60-1.66 eV region. Based on the angular dependence of the separation between the peaks, we explain the two features in terms of optical absorption involving the quantum-well exciton and the cavity mode. The minimum separation between them (5 meV at an angle of about 25°) corresponds to the maximum exciton-cavity coupling, as confirmed by reflectivity measurements performed under similar conditions. Our results show that PLE can complement or even substitute for other techniques that probe the optical properties of microcavities.