Optical orientation and thermal relaxation of excitons in semi- magnetic CdMnSe/ZnSe quantum dots — •Thomas Schmidt 1 ,

EPIII, Universit¨at Wurzburg¨ , Am Hubland, 97074 Wurzburg,¨ GermanyPolarization dynamics of quantum dots (QDs) represent actually anintensely studied field of research. Of special interest are semimagneticquantum dots due to their distinct magnetic properties caused by theinteraction of carrier spins with the Mn spin system. It is clear that withdecreasing Mn content the semimagnetic properties are reduced. Wehave studied the polarization dynamics of a series of optical orientationand thermal relaxation of excitons in CdMnSe/ZnSe quantum dots fordifferent Mn contents ranging from 0 to 2%. From the dependence ofthe polarization on the magnetic field strength we determined the exci-ton g factors of the QDs for different Mn contents and the relevant spinrelaxation times. In particular, we have been able to resolve the signreversal of the g factor. In QDs with negligible g factor the polarizationproperties are dominated by the optical orientation of the excited light.The spin relaxation times extracted from the thermal relaxation dependsensitively on the Mn concentration in a range of a few picoseconds.HL 35.2 Wed 14:45 POT 151Whispering gallery modes in ZnSe/MgZnSSe-microdiscs withCdSe quantum dots at room temperature — •Johannes Ren-ner