Résumé
We report on the observation of the teraherz quantum beats in the four level system consisting of the heavy hole exciton states coupled to the magnetic ions via exchange interaction. Such states are prepared in CdMnTe quantum well where the magnetic field is applied at 45 degrees with respect to the sample surface normal. We show that the time-resolved Kerr rotation signal provides the information on the dynamics of the spin transitions in this complex system via circular dichroism (i) which makes the signal oscillate when the spin polarization created by the circularly polarized pump pulse precesses in the magnetic field; the linear dichroism (ii) which gives rise to the signal even in the absence of the net spin polarization, e.g. when the exciton states are excited by the linearly polarized pump pulse. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.