| The coupled single quantum dot (QD)-microcavity system, served as the solid implementation of cavity quantum electrodynamics (CQED), has recently attracted much interests and research effort due to its potential applications in future optoelectronic devices and quantum information processing. In this dissertation, we report our studies on optical properties of a single QD coupled to a micropillar microcavity. In contrast to the traditional sample growth by MBE system, which has low sample productivities, we use MOCVD system to grow the cavity QD samples. After the sample growth, we used FIB technique to etch the sample into micropillars, which contain a single layer of InGaAs QDs in the center cavity region. For the optical study, we first measured the temperature dependent photoluminescence (PL) of a single micropillar. By tuning the temperature, we were able to tune the energy detuning between single exciton transitions of a single QD and the cavity mode, and we observed the crossing behavior at the spectra resonance region, which indicated the system was in the weak coupling regime. In the weak coupling regime, we observed the strong Purcell effect, i e, the enhancement of the spontaneous emission (SE) rate of a single QD by temperature tuning. Theoretically, we modeled our system using a three-level rate equation, and by calculating the integrated intensities of exciton emission at different detunings, we extracted the effective Purcell factor of3.8±1.2.Considering that temperature tuning method does not provide access to manipulate the spin degree of freedom of excitons, we proposed a new method that study and control the QD-cavity mode coupling effect by means of external magnetic field. In order to get a deeper understanding of the magnetic effect on QD exciton transitions, we firstly performed the magneto-optical studies on single InGaAs/GaAs self-assembled QDs. We observed the exciton Zeeman splitting and diamagnetic shift of a single QD under magnetic field, and the exciton g factor and diamagnetic coefficient was extracted by fitting the magnetic field dependent PL energies. By comparing with theories, we discussed on the effect of QD size, shape and composition on these two parameters. Based on these work, we investigated the single QD exciton-cavity mode coupling effect under external magnetic field. By first time we observed the interaction of Zeeman splitted exciton spin states with the cavity mode and realized the selective enhancement of the SE rate of the exciton state with specific spin configuration by means of magnetic manipulation of Purcell effect. In this sense, single QD emission with higher circular polarization degree under non-polarized excitation was realized. Considering the Zeeman effect, we proposed a four level rate equation which includes the weak coupling effect to describe the coupled system, and calculated both of the emission intensities of the spin split exciton states. The theoretical results fit quantitatively well with our experimental data, thus demonstrated the effective control of the magnetic field over the coupled QD spin states-cavity mode system. Our results have high potential to open up a way to novel quantum light sources and quantum information processing applications based on CQED effects. |
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