EXCITON PHOTON COUPLING IN GAAS BULK MICROCAVITIES

A great interest in the study of exciton-photon coupling in resonant o ptical media such as semiconductor microcavities is currently developi ng both in experiments and in theory. We investigate the spectral resp onse of a new semiconductor quantum system in which the cavity materia l itself is the active medium. If the Fabry-Perot quasi-mode is carefu lly tuned on the excitonic transition of the cavity bulk material, str ong exciton-photon coupling takes place and produces new features such as a Rabi-like splitting as large as that observed in quantum well mi crocavities and comparable optical absorption. In addition, the polari tonic spatial dispersion and the quantization of the centre-of-mass mo tion introduce remarkable fine structures which are absent in the quan tum well ease. We demonstrate the above effects from a spectroscopic a nalysis of GaAs cavities, using standard reflectance and photoluminesc ence techniques. The experimental results are further clarified with t heoretical calculations performed with an adapted transfer-matrix appr oach. The case of semi-cavities is finally considered and a new way to control the exciton-photon interaction in our system is achieved tail oring the photonic wave function with a change in the reflectivity pha se of the mirrors.