Physical review. B, Condensed matter
Signatures of correlations in intensity-dependent excitonic absorption changes
T. Meier, S. W. Koch, Peter Brick, Claudia Ell, G. Khitrova, H. M. Gibbs
Abstract
The intensity dependence of pump-induced excitonic absorption changes is studied in high-quality ${\mathrm{In}}_{0.04}{\mathrm{Ga}}_{0.96}\mathrm{As}$ quantum wells for different detunings and polarization configurations. For resonant excitation with increasing pump intensity a saturation of both the exciton bleaching and the induced absorption due to two-exciton resonances is observed, whereas for pumping below the exciton a characteristic polarization dependence of higher-order contributions to the optical Stark effect is found. Microscopic calculations including Coulomb correlations show that the experimental observations can be described by the coherent dynamics of single- and two-exciton resonances up to fifth order in the optical field.