Excitation-induced dephasing and biexcitonic effects in the coherent control of excitonic polarization in pulse-transmission experiments

Optical coherent manipulation of excitonic polarization is studied in pulse-transmission experiments at medium to high excitation intensities. As a well-defined model system a ZnSe single-quantum well is used. It is found that for constant excitation intensities the dephasing time of the polarization in the sample changes significantly if the cases of coherent amplification and destruction are compared. This effect is explained in terms of an excitation-induced dephasing. The change of the dephasing time of the polarization is quantified. Furthermore, the simultaneous excitation of the exciton and exciton-biexciton resonances is shown to strongly influence the signal of the polarization in the coherent-control experiments. Both the excitation-induced dephasing and the biexcitonic effects are simulated by use of phenomenological models which give a good agreement with the experiments.