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

The self-diffraction four wave mixing signal from excitonic transitions in GaAs quantum wells is investigated experimentally as a function of arbitrary linear polarization orientation of the incident light pulses. The polarization of the diffracted signal, and the phase of quantum beats between light and heavy hole excitons, are shown to be strongly 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 the theoretical model occur.