Optically Induced Polarization Anisotropy in Porous Si

Strong surface-plane polarization anisotropy of the probe photoluminescence induced by a polarized cw pump beam has been observed in porous Si. At room temperature the effect is simultaneous with the pump and depends strongly on its intensity. At low temperature long lived anisotropy of the photoluminescence polarization is induced by a preliminary soaking with polarized light. Both effects are described by the selective excitation of nonspherical Si crystals aligned along the vector polarization of the pumping light together with complete suppression of the photoluminescence by nonradiative Auger processes in crystals with an additional hole and/or electron.