We report on optical orientation of excitons and trions (singly charged exciton) in individual charge-tunable self-assembled InAs/GaAs quantum dots. When the number of electrons varies from 0 to 2, the trion photoluminescence under quasi-resonant excitation gets progressively polarized from zero to ≈100%. We discuss this behavior as the efficient quenching of exciton spin quantum beats in anisotropic quantum dots due to the trion formation. This result indicates a long hole-spin relaxation time larger than the radiative lifetime, confirmed by time-resolved photoluminescence measurements carried out on a quantum dots ensemble.
We investigate the influence of an electric field on the optical properties of single quantum dots. For sample made of III-V compounds micron-size electro-optical structures were produced in order to apply an electric field in the dot plane. For several individual dots lines significant variations of the anisotropic exchange splitting with the field were observed. On sample made of II-VI compounds we demonstrate the influence of electric field fluctuations on the luminescence of a single quantum dot.
We describe the physics of cavity polaritons in semiconductor micropillars. Cavity polaritons are exciton-photon entangled states arising from the strong coupling between excitons and the optical modes of a cavity. In micropillars, the photon three-dimensional confinement results in a discrete spectrum of 0D polariton states. Characterization of the linear properties of these micropillars will be presented. Then we will show how this system can be used to generate parametric photons and to obtain polariton lasing.
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