Exciton-photon dynamics in weakly and strongly excited semiconductor microcavities

We report on the optical response of a semiconductor microcavity featuring a strong exciton-photon coupling. The weak excitation regime is investigated experimentally by means of time-resolved transmission and four-wave mixing experiments. The influence of electronic disorder on the coherent exciton-photon dynamics is discussed in terms of tl-ie solutions of the Maxwell-Bloch equations. The high excitation regime is investigated by using transient sub-picosecond pump-probe experiments. Optical amplification of the probe beam (up to a factor of five), as well as a fundamental change of the optical spectra: have been found close to and above the exciton saturation density. The observed oscillations are corresponding to the Rabi frequency of the excitons in the pump field.