We present a quantization procedure for the electromagnetic field in a circular cylindrical cavity. A complete set of vector mode functions satisfying the boundary conditions is obtained utilizing field decomposition. The quantized electromagnetic Hamiltonian is then derived. The conditions for enhancement and inhibition of the spontaneous emission rate per second by an atom inside the cavities are presented in the electric-dipole approximation. Emission is inhibited completely if the cavities are very small. Generally, the behavior is quite complicated; there are many sharp peaks at resonance points and minimal values approach that in free space as the radius of the cavities becomes large.
We present a quantization procedure for the electromagnetic field in a circular cylindrical cavity. A complete set of vector mode functions satisfying the boundary conditions is obtained utilizing field decomposition. The quantized electromagnetic Hamiltonian is then derived. The conditions for enhancement and inhibition of the spontaneous emission rate per second by an atom inside the cavities are presented in the electric-dipole approximation. Emission is inhibited completely if the cavities are very small. Generally, the behavior is quite complicated; there are many sharp peaks at resonance points and minimal values approach that in free space as the radius of the cavities becomes large.
The conditions for enhancement and inhibition of the spontaneous emission rate per second by an atom inside coaxial cavities are investigated in the electric-dipole approximation. A complete set of vector mode functions satisfying the boundary conditions is obtained utilizing field decomposition, which is needed to quantize the electromagnetic field. The behavior of the emission rate is generally quite complicated; there are sharp peaks at many resonance points, and the minimal values approach unity as the radius of the cavities increases. Emission is usually inhibited completely if the radius is very small. However, under certain conditions, one being a small radius, there is the possibility of very large emission due to the TEM mode.
The normal modes of electromagnetic fields satisfying three different boundary conditions are constructed systematically. For each of these cases, cavity quantization of the electromagnetic fields is carried out explicitly. It is possible, using normal modes, to perform a unitary transformation of the minimal-coupling Hamiltonian of an atom inside the cavity to a multipolar form. It is shown that the boundary condition plays an important role in the transition rates for the spontaneous emission by the atom. Some explicit calculations are carried out for several different boundary conditions. These results become consistent with those for free space in the large-box limit.
Abstract. We present a general formalism for studying the emission rate of an atom inside a high Q-factor quantum cylindrical resonator. The electromagnetic field structure inside such closed resonator is de-rived. Then the cavity modes are quantised, allowing the position-dependent atomic emission rate to be calculated. Depending on the circumstances, the atomic emission rate may be increased or reduced, and in extreme cases is completely suppressed. Especially, in the quantum size system, the atomic emission rate is possible only via a few cavity modes. The calculations are carried out for the sodium atoms immersed in an empty quantum size resonator. 1.
This thesis is concerned with the theory of spontaneous emission in the context of cavity QED and the guiding of atoms by laser light in confined geometries. We focus on three different geometrical shapes of waveguide, namely the parallel plate guide and two kinds of cylindrical waveguide: one with a rectangular cross section and another with a circular cross section. These waveguides are assumed to be characterised by two distinct properties. Firstly, all three types of guide have perfect conductor boundary conditions, which means that the guide walls are infinitely conducting and, consequently, lossless. Secondly, the guides are assumed to have subwavelength dimensions (less than the atom electric dipole transition wavelength #lambda#). The first consequence of this is that the spontaneous emission process is possible only via a few cavity modes. For each type of structure, we examine the confinement of electromagnetic fields within it and proceed to quantise these fields by following the standard procedure, incorporating the boundary conditions at the guide walls. This allows the position-dependent spontaneous emission rate to be evaluated for an electric dipole located at an arbitrary point within the guide. Asymptotic limits of the spontaneous emission rate are then derived which serve as useful checks of the calculations. For the rectangular guide, we are able to recover the results appropriate for the parallel-plate case when side a of the rectangular cross section becomes large, while side b is kept fixed. For the circular guide, we are able to recover the results appropriate for the free space case when the radius of the guide becomes large. The second part of the thesis deals with the theory of the motion of atoms in the spatially varying light fields inside the three different shapes of waveguide. In each structure we examine the forces that act on the atom and solve the equation of motion leading to the atom dynamics when an electric dipole within the guide is subject to an excited p-polarised cavity mode. The characteristics of the atomic motion in the guide in the presence of a cavity mode are then explored. We show that under these conditions the atom becomes subject to a transverse dipole potential and a dissipative force, both of which vary across the guide and are also functions of the atom velocity along the mode propagation direction. The dipole potential is responsible for the transverse trapping (and hence the channelling) of atoms at specific regions of the cross section, while the dissipative force controls the longitudinal motion of the channelled atoms. The conditions facilitating atom guiding are explored using typical parameters for sodium atoms in guides of subwavelength dimensions. The roles of the van der Waals and Casimir-Polder potentials on the atomic motion in waveguides is clarified theoretically in the context of the parallel-plate guide and we show that such potentials are effective only at relatively short distances from the guide walls. Finally, we show that atomic motion in a hollow circular guide is subject to a quantised torque arising from the orbital angular momentum effects associated with any excited waveguide mode of order l > 0. We find that an appropriately detuned atom immersed in such a mode may be trapped radially in a vibrational state and be made to exhibit novel rotational effects associated with the light torque, including a rotational frequency shift. (author)
Abstract We investigate a two-level atom interacting with a massless real scalar field inside an infinitely long cylindrical cavity, and calculate separately the contributions of vacuum fluctuations and radiation reaction to the mean atomic energy-change rate when the atom moves along the cavity axis. Using the formalism suggested by Dalibard, Dupont-Roc, and Cohen-Tannoudji, we analyze both inertial and uniformly accelerated motion, and discuss the behavior in the low-acceleration and high-acceleration regimes. For the inertial atom, we further introduce a finite cavity quality factor Q to phenomenologically account for cavity dissipation, which regularizes the resonant singularity of the ideal lossless cavity and yields finite resonant peaks. For a uniformly accelerated excited-state atom in the low-acceleration regime, the energy-change rate remains finite at the nominal resonance points, but exhibits pronounced oscillatory enhancement near resonance. In certain parameter regions, the cavity result can exceed both the corresponding inertial result in the same cavity and the uniformly accelerated result in free space, revealing the combined effect of acceleration-induced broadening and the discrete transverse mode structure of the cylindrical boundary. In the high-acceleration regime, a ground-state atom may undergo spontaneous excitation, while the cavity resonance structure is strongly suppressed and the energy-change rate gradually approaches the corresponding free-space value. These results show that the cylindrical geometry can significantly reshape the radiative response of accelerated atoms, enhancing acceleration-induced effects at low acceleration while washing out cavity-induced resonances at high acceleration.
Abstract The electromagnetic field is quantized on the basis of the complete set of spatial modes of a plane dielectric slab of arbitrary thickness and refractive index but infinite transverse dimensions, located in otherwise empty three-dimensional space. The vacuum field fluctuations and spontaneous emission rates are evaluated as functions of position both inside and outside the slab. The source-field operator is derived for emission by atoms inside the slab, in the direction perpendicular to its surfaces. Particular attention is given to the possibility of suppressing spontaneous emission by placing atoms in, or close to, a dielectric slab.