Intrinsic non-linearities in exciton-cavity-coupled systems

We investigate the mechanisms leading to the optical non-linearities observ ed on a strongly excited semiconductor microcavity containing quantum wells . This study of a coupled exciton-cavity system is possible owing to the av ailability of a sample of exceptionally high quality, permitting to exclude effects of disorder and inhomogeneous broadening. Sub-picosecond pump and probe experiments are performed, in the regime of an incoherent exciton gas of high density. For such a gas the dephasing due to collisions is not eff icient enough to cause the break-down of the strong coupling and hence the collapse of the Rabi splitting. Phase-space filling and exchange effects ar e the dominant mechanisms. (C) 1999 Elsevier Science B.V. All rights reserv ed.