Circular dichroism in InAs GaAs quantum dots: Confinement-induced magnetism

Abstract

Self-assembled InAs GaAs quantum dots (QDs) are studied by means of circular polarization-resolved photoluminescence and pump-probe differential reflectivity as a function of the excitation density using a linear polarized pump laser. We observe an unexpected large circular polarization anisotropy, which decreases with increasing excitation density for both experimental techniques. Comparison of the respective polarization degrees reveals a ratio of approximately 0.2. Moreover, the reflection measurements reveal circular dichroism with a ratio of Θ+ Θ- =1.16. Circular dichroism in semiconductor QDs can be explained by the induced magnetism as a result of light confinement in QDs, providing an anisotropic coupling between the pump-induced QD exciton and the circularly polarized probe field. © 2006 The American Physical Society.