Kerr rotation induced by femtosecond pulses in a CdMnTe quantum well embedded in a microcavity is studied under an in-plane magnetic field. Due to giant Zeeman splitting in the diluted magnetic quantum well, in this system we deal with two spin splitted exiton states coupled to the cavity mode. For such a microcavity operating in the strong coupling regime, the polariton spin beats in the time-resolved Kerr rotation signal can be expected at three distinct frequencies. Two of them are observed in our experiments, in a excellent agreement with the theoretical calculation in the framework of the polariton spin density matrix, which accounts for the finite lifetimes of exciton and photon states.

The injection of nonequilibrium carriers in a paramagnetic diluted magnetic semiconductor in the presence of magnetic field may induce a spontaneous magnetization patterning. This phenomenon is studied in CdMnTe quantum wells using time resolved Kerr rotation experiments and the model based on the coupled rate equations for interacting electron and magnetic ion spins is developed.

Rabi oscillations are observed in the optically induced time-resolved Faraday rotation from a strong-coupling microcavity. They reveal the dynamics of the excitonic part of the polariton state, including the spin related information. The oscillations of the same period are observed at both circular and linear pumping, suggesting the splitting of the ground polariton state into a linearly polarized doublet.

Transverse electron and hole spin relaxation times were measured in both parts of a generic spintronic structure device consisting of two thin layers: diluted magnetic Cd0.96Mn0.04Te (spin aligner) and a layer non-magnetic CdTe (spin accumulator). By using time-resolved magnetoptical Kerr rotation as a fast time-resolved magnetization probe, we find that the carriers in Cd0.96Mn0.04Te lose their initial spin coherence within similar to 1ps. The undoped spin accumulator is characterized by relatively long electron spin relaxation time that of the order of several hundreds ps.

Magnetization patterning by injection of nonequilibrium electron spins in paramagnetic diluted magnetic semiconductors is studied theoretically. The system is shown to undergo an instability in a region of the parameter space defined by the carriers generation rate and magnetic field. The bifurcation is found to be of subcritical nature. Existing experimental results are examined within this model and experiments are proposed.

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.

CdMnTe quantum well embedded in CdMgTe/CdMnTe microcavity is studied by time-resolved Kerr rotation experiments under in-plane magnetic field and quantum beatings corresponding to at least three distinct frequencies are observed. Whereas the lowest gigahertz frequency is clearly identified with Mn spin precession in the quantum well, terahertz beatings can be due to both polariton formation and valence band states mixing in the magnetic field. However, the experiments indicate unambiguously that there is no beatings between coherently excited polariton states in the absence of magnetic field, in contrast with the proposed model, which predicts the beatings at Rabi frequency in zero field. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.