Photoinduced magneto-optic Kerr effects in asymmetric semiconductor microcavities

Giant photoinduced magneto-optic Kerr effects are predicted and measured in asymmetric semiconductor microcavities with a totally reflecting rear mirror operated in the limit of the strong coupling regime. The microcavity is modeled by two coupled Fabry-Perot cavities and use is made of the optical scattering matrices to derive its characteristics. The giant photoinduced rotations and phase changes are traced to the saturation, blueshift, and pseudo-Zeeman splitting of the exciton transition. Modeling the lower and upper polariton transitions by two different two-level systems qualitatively accounts for the main spectral features: the photoinduced Kerr rotations and phase changes are due to the modifications of the coupling existing between the cavity and exciton modes, due to the photoinduced changes of the exciton characteristics. The influence of spin relaxation on the rotation and ellipticity spectra is also analyzed; it confirms the gyrotropic nature of the interaction which depends strongly on the difference between the densities of counter-rotating circularly polarized excitons and only weakly on their sum as is the case in previous isotropic studies. Measurements of photoinduced Kerr rotations performed at a temperature of 50 K in a microcavity containing a single semimagnetic semiconductor quantum well confirm the effectiveness of the effect with polarization rotations of 10° around the lower polariton frequency at a pump fluence of only 2 μ${\mathrm{J}/\mathrm{c}\mathrm{m}}^2$.