The Lifetime Distribution Of Excited Atoms In Microcavity

The excited Rydberg atom can be used to sensitively probe the radiation and various of fields due to its abnormal property, e.g., its sensitivity to outer environment and its bigger semidiameter. How yielding and remaining it in high excited states is a challenging subject for interference manipulate and precise measurements. The relevant 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 determined by 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 and lifetime distribution of Rydberg atoms with different polarized directions placed in a confined geometry where the vacuum fluctuations are altered interaction between the electron-magnetic field and atoms.Recently, since the fast development of experimental technique and practical theoretical applications, much attention has been paid to the point that the spontaneous emission rate and lifetime distribution of excited atoms can be modulated by the altering the outer environment conditions. The tide of the photonic crystals and the micro-device to capture excited atom have also greatly promoted this investigation.In this submitted thesis, our main works are described as follows:(1). The Rydberg atoms are represented in terms of second quantalization, 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 material microcavity sandwiched by two dielectric semi-infinite substrates with arbitrary refractive indices or in an optical microcavity (OM) made by two perfect parallel mirrors at different polarization orientations of atomic dipole moments provided certain boundaries conditions.(2). The formulas of the quantum electrodynamics are applied to calculate the spontaneous emission rate and lifetime distributions of excited atoms with different dipole moment polarizations in symmetric and ansymmetric dielectric microcavities. Our calculations show that the decay property and the lifetime distribution depend not only on the width of the microcavity, the refractive index of medium surrounding atoms, but also on the polarized orientation of atomic dipole moments.(3). As a comparison, we calculate and analyze the spontaneous emission rate and lifetime distributions of excited atoms with different dipole moment polarizations in an optical microcavity (OM) that made by a medium with a refractive index n sandwiched between two perfect parallel mirrors. The changes of the decay property and the lifetime distributions with the variance of the width of the cavity, the refractive index of medium surrounding atoms and the polarized orientation of atomic dipole moments are analyzed also.(4). The decay properties of an polarized atom in the vicinity of a perfect reflecting mirror is calculated using Fermi's golden rule and Green function approach. The photon closed-orbit theory is successfully used to explain this phenomenon. It is found the polarized orientation of the atom can control the atomic spontaneous emission process by varying the rates of photon wanes returning back.This thesis is divided into six chapters. The first chapter is summarization which introduces and reviews in brief 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 derive the formulas of the decay rate of an excited atom in both a dielectric microcavity and an optical cavity based on the cavity quantum electrodynamics provided certain boundary conditions of the system. In the third chapter, we studied theoretically the SE and LD of an assembly of atoms with different polarizations in a symmetric or asymmetric dielectric microcavity. A switching effect between the inhibition and enhancement of SE rates, which mainly originates from the polarization of the dipole moment of atoms, could be found under these two conditions. This phenomenon can be explained as below: on one hand, the SE rates of all atoms polarized perpendicular to the cavity are inhibited intensively because of the discontinuity of the electric fields, i.e., the abrupt change of the normal components of the electric fields at the interfaces between the medium surrounding atoms and the dielectric background medium. On the other hand, when the atoms polarized parallel to the tangential direction of the interfaces, the discontinuity of the electric fields does not bring any influence.In order to make a comparison with the results gotten in dielectric microcavity, we calculated theoretically the SE and LD of an assembly of atoms with different polarizations in an optical microcavity. The same as in a dielectric cavity, we could find the switching effect again when the width of the OM is large enough. The SE properties of polarized atom in the vicinity of a perfect reflecting mirror is calculated using Fermi's golden rule and Green function approach in the fifth character. The results exhibit damping sine-like oscillations pattern which depend sensitively on the atomic position and the polarized orientation of atomic dipole moments. For the polarized direction parallel to the mirror plane, the oscillation is the greatest, and with the increase of the polarized angle, the oscillation in the decay rate becomes decreased. While for the perpendicular polarized direction, the oscillation is nearly vanished. The photon closed-orbit theory is successfully used to explain this phenomenon. It is found the polarized orientation of the atom can control the atomic spontaneous emission process by varying the rates of photon waves returning back.As the conclusion, in the last chapter, we briefly summarize the total subject. In the end of this thesis, we give an inspection to the challenge and the application of this theory.