Influence Of Dielectric Cavity On The Spontaneous Emission Rate Of Atom

The excited Rydberg atom can be used to sensitively probe the radiation and various of fields due to its abnormal property. How to yield it and remain it in high excited states as possible as long is an important subject for interference manipulate and precise measurements. The relavant investigations have played critical role in new techniques such as atom-chip, photonic crystals. Lots of interesting explorations have demonstrated that the spontaneous emission rate of atom depends on the material environment. The lifetime of the excited atom is related to the spontaneous emission of atom, that is, the spontaneous emission can be described by the interaction of an atomic dipole with the quantized electromagnetic vacuum field. Therefore, it is possible to modify the emission decay rate of Rydberg atoms placed in a confined geometry where the vacuum fluctuations are altered interaction betwwn the electronmagnetic and atoms..Recently, along with the fast development of experimental technique and practical application, much attention has been paid to the point that the spontaneous emission rate can be modulated by the material environment. The tide of the photonic crystals and the micro-device to capture excited atom has greatly promoted this investigation.In this submitted thesis works, we present theoretical calculations of the spontaneous emission rate of excited atom in dielectric cavity based on the formulas of the cavity quantum electrodynamics combining together with scaling transformation and spectral analysis method. We investigate two systems in which the excited atom is placed in the symmetric dielectric cavity and the asymmetric one, respectively. The main works are as follows:(1). The atoms are represented in terms of second quantinization, while electromagnetic field is denoted in field operator by an quantized process.Then the formulas of the spontaneous emission rate of excited atom in dielectric cavity provided certain boundaries conditions.(2). The formulas of the quantum electrodynamics are applied to calculate the spontaneous emission rate of excited atom in symmetric dielectric cavity. The characteristic frequencies are extracted from the damping oscillations of spectra of spontaneous emission by Fourier transform, which correspond to the classical actions of allowed photon's closed orbits.(3). As a comparison, we calculate and analyze the effect of the medium refractive index for an excited atom placed in asymmetric dielectric cavity. Other than the case in symmetric cavity, the damping oscillations of spontaneous emission rate of excited atom exibits more strongly.This thesis is divided five chapters. The first chapter is summarization, which introduces and reviews the background and the development of the spontaneous emission theory, the cavity quantum electrodynamics and the classical closed-orbit theory.In the next chapter, we derived the formulas of the decay rate of an excited atom based on the cavity quantum electrodynamics provided certain boundary conditions of the system.The third chapter is our calculation. The formulas of the quantum electrodynamics have been applied to compute the spontaneous emission rate of excited atom in symmetric dielectric cavity. The results display damping oscillating patterns which depend sensitively on the scaling parameter and dielectric geometrical structure. Compared with the case that the emitting atom is immersed in dielectric, the spontaneous emission rate is depressed obviously and the center or the mean value of the oscillations is intimately related to the real refractive index of the local position where the atom is. In order to explain this phenomenon, we extract the corresponding frequencies of the oscillations by Fourier transform.and utilize the closed-orbit theory to explain the classical trajectories of the emitted photon. We find that the oscillations can be represented in terms of the closed-orbits of the photon motion constrained in dielectric cavity.In chapter four, we consider the asymmetric case which is the excited atom in the asymmetric dielectric cavity in the same method as in previous chapter. Compare with the excited atom in symmetric dielectric cavity, we anlyze the effect of dielectric refractive index .As the conclusion, in the last chapter, we briefly summarize the total subject. In the end of this works, we give an inspection to the challenge and the application of this theory.