Spin dynamics of cavity polaritons

We have studied polariton spin dynamics in a GaAs/AlGaAs microcavity by mea ns of polarization- and time-resolved photoluminescence spectroscopy as a f unction of excitation density and normal mode splitting. The experiments re veal a novel behavior of the degree of polarization of the emission, namely the existence of a finite delay to reach its maximum value. We have also f ound that the stimulated emission of the lower polariton branch has a stron g influence on spin dynamics: in an interval of similar to 150 ps the polar ization changes from +100% to negative values as high as -60%. This strong modulation of the polarization and its high speed may open new possibilitie s for spin-based devices. (C) 2001 Elsevier Science Ltd. All rights reserve d.