Direct observation of excitonic Rabi oscillations in semiconductors

We observe multiple excitonic optical Rabi oscillations in a semiconductor quantum well. Up to eight oscillation periods of the heavy-hole exciton den sity on a subpicosecond time scale are observed. An approximate linear depe ndence of the oscillation frequency on the light field amplitude is establi shed. The experiment is based on a two-color detection scheme which allows for the observation of the heavy-hole exciton density via transmission chan ges at the light-hole exciton. The observations are in good agreement with theoretical computations based on multiband semiconductor Bloch equations.