Polarization dynamics in self-assembled CdSe/ZnSe quantum dots: The role of excess energy

The polarization dynamics of zero-dimensional exciton emission is studied for CdSe/ZnSe quantum dots going systematically from strictly resonant to nonresonant excitation. Independent on the excess energy, no transient decrease of the polarization is found for ground state exciton emission. However, the absolute value of the polarization degree exhibits a strong nonmonotonic dependence on the excitation energy. We demonstrate that the initial loss of polarization after nonresonant excitation can be minimized if the exciton excess energy corresponds to an integer multiple of LO-phonon energies.