INTENSITY DEPENDENT 4-WAVE-MIXING POLARIZATION RULES IN QUANTUM-WELLS

The self-diffraction four wave mixing signal from excitonic transition s in GaAs quantum wells is investigated experimentally as a function o f arbitrary linear polarization orientation of the incident light puls es. The polarization of the diffracted signal, and the phase of quantu m beats between light and heavy hole excitons, are shown to be strongl y dependent on the magnitude of excitation intensity. The experimental results observed for excitation densities above 2 x 10(9)cm-2 are in accordance with theoretical conceptions of the polarization selection rules for light and heavy hole exciton transitions in a quantum well. For lower excitation, remarkable deviations from the predictions of th e theoretical model occur.