Quantum State Regulation And Optical Properites In Quantum Dot-Cavity Coupling System

Quantum dots-nanocavity coupling system, on the one hand, due to the nanometer level have unique optical properties under the limited, on the other hand, with the advantages of high integration density, efficiency and construable, in recent years have become a research hotspot in the field of quantum information. Supported by the National High Technology Research and Development Program of China (Grant No.2009AA03Z405) and National Natural Science Foundation of China (Grant Nos.60971068, 61275201,61372037), this doctoral thesis mainly focus on the quantum state regulation and optical properties of coupled quantum dots-cavity systems. The main achievements and innovations are as follows:1) Two-photon emission characteristic of biexciton quantum dot-cavity system. Adopting the phonon-assisted method, we study the steady-state fluorescence spectrum characteristics of biexciton quantum dot-cavity system, proving that the phonon interaction broke the symmetry structure of emission peak intensity, which is consistent with experimental results have been reported. And the phonon effect on the number of photons isn’t obvious.Under pulse excitation, dynamic changes in time domain were calculated, and we find the four-level structure of quantum dots lead to the increase the width of the photon number oscillation. With the increase of pulse width, the maximum photon numbers would climb up and then decline.Finally we research the pulse sequence excitation situation and all-optical switch application of the system.2) The dynamic characteristics of multiple quantum dots-cavity system. We adopt Monte Carlo wave function method to research the influence of multiple quantum dots co-operative on the photon numbers under pulse excitation, and find that the photons oscillation frequency increase with the rise of quantum dots number. Moreover we analyze the similarities and differences of the photon number change under microcavity and quantum dots driven respectively. Combined with equations of motion and quantum regression theorem, the time dependent fluorescence spectra are calculated. The optical properties of the two quantum dots and single quantum dots under long or short pulse are researched, showing that under coherent excitation pulse width only affects the process of fluorescence spectrum, and not change the final steady state, and under coherent excitation pulse width not only affects the process of fluorescence spectrum, but also change the final steady state.3) Single photon emission characteristic of the coupled double quantum dots-cavity system. Under cavity quantum electrodynamics framework, the interaction between double quantum dots are taken into account to study the photon statistical properties. Our work find that when the direct coupling between double quantum dots exist, under specific laser frequency detuning strong sub-Poisson photon distribution characteristics can be achieved, and both in quantum dots-cavity system strong coupling and weak coupling regime we can obtain single photon emission. We also studied the probability of several photon states, and find that the coupling between quantum dots has destroyed the symmetry structure of the probabilities around laser frequency. The non-ideal situation where two QDs aren’t identical are also discussed, indicating that our proposed scheme can realize single photon emission in a large QDs difference variation range.4) Spin initialization of the quantum dot-plasmonics system. We theoretically investigate the preparation of spin in a hybrid system consisting of a quantum dot (QD) and metal-dielectric interface. Based on the Drude model of metal permittivity, a cavity quantum electrodynamics (CQED) method is used to analyze the influence of surface plasmon polaritons (SPPs) on the emission of QD. Due to coupling between spin and interface (with a different value along different direction), a fast initialization beyond the GHz range can be achieved with high fidelity (99.5%) at reasonable external parameters, under both continuous wave and pulse excitation. Compared with material properties, the distance between QD and metal layer are the most important factor that affect the spin initialization.5) Quantum dot-metal torus pair system. Combined with finite element method and quantum master equation, we obtain the cavity quantum electrodynamics description of the quantum dot-metal torus pair system by fitting the absorption cross section. Further we consider the influence of laser intensity on the fluorescence spectrum and the saturated quantum dot caused by the large intensity.