BULK EXCITON POLARITONS IN GAAS MICROCAVITIES

The optical properties of excitons in thin layers are significantly di fferent from those in bulk crystals. In particular, we study the case of a bulk material of thickness comparable with the wavelength of the excitonic transition confined on one or on both sides by appropriate B ragg reflectors. If-the cavity resonance quasimode is carefully tuned on the excitonic transition, strong exciton-photon coupling takes plac e and produces a Rabi-like splitting as large as that observed in quan tum-well-implanted microcavities and comparable optical absorption. In addition, the polaritonic spatial dispersion and the quantization of the exciton center-of-mass motion introduce remarkable fine structures which are absent in the quantum-well case. We demonstrate the above e ffects from a spectroscopic analysis of GaAs cavities and compare them with those displayed by quantum-well-implanted microcavities.