Optical properties of an atom in the vicinity of a metal or dielectric are different from those in free space. The spontaneous decay of an atom with two degenerate levels is studied, where the relaxation operator is obtained as a function of the atom-surface separation and the complex bulk dielectric of an excited state \ensuremath{\Vert}${j}_{e}$${m}_{e}$〉 appears to depend on the magnetic is derived, and from the rotational symmetry with respect to the surface normal it is found . A general expression for the fluorescent radiation field in the far zone is then derived, which incorporates the polarization properties of the fluorescence, as they are modified by the presence of the dielectric. It is shown that the angular distribution of the emitted intensity depends strongly on \ensuremath{\epsilon}(\ensuremath{\omega}), and it is pointed out how information about the substrate, e.g., \ensuremath{\epsilon}(\ensuremath{\omega}), can be extracted from the temporal statistical behavior of the emitted photons. It is emphasized that the major surface effects are purely geometrical, despite the essential quantum nature of the problem.
Optical properties of an atom in the vicinity of a metal or dielectric are different from those in free space. The spontaneous decay of an atom with two degenerate levels is studied, where the relaxation operator is obtained as a function of the atom-surface separation and the complex bulk dielectric of an excited state \ensuremath{\Vert}{j}_{e}$${m}_{e}〉 appears to depend on the magnetic is derived, and from the rotational symmetry with respect to the surface normal it is found . A general expression for the fluorescent radiation field in the far zone is then derived, which incorporates the polarization properties of the fluorescence, as they are modified by the presence of the dielectric. It is shown that the angular distribution of the emitted intensity depends strongly on \ensuremath{\epsilon}(\ensuremath{\omega}), and it is pointed out how information about the substrate, e.g., \ensuremath{\epsilon}(\ensuremath{\omega}), can be extracted from the temporal statistical behavior of the emitted photons. It is emphasized that the major surface effects are purely geometrical, despite the essential quantum nature of the problem.
Abstract : Optical properties of an atom in the vicinity of a metal or dielectric are different from those in free space. The spontaneous decay of an atom with two degenerate levels is studied, where the relaxation operator is obtained as a function of the atom-surface separation and the complex bulk dielectric constant epsilon(omega). The Einstein coefficient A(m)(e) of an excited state jeme appears to depend on the magnetic quantum number me. A sum rule for A(m)(e) is derived, and from the rotational symmetry with respect to the surface normal it is found that A(m)(e) = A(-m)(e). A general expression for the fluorescent radiation field in the far zone is then derived, which incorporates the polarization properties of the fluorescence, as they are modified by the presence of the dielectric. It is shown that the angular distribution of the emitted intensity depends strongly on epsilon(omega), and it is pointed out how information about the substrate, e.g., epsilon(omega), can be extracted from the temporal statistical behavior of the emitted photons. It is emphasized that the major surface effects are purely geometrical, despite the essential quantum nature of the problem. Keywords: Spontaneous decay, Atomic fluorescence, Atom near metal surface, Absorbing dielectric, Einstein coefficient, Magnetic quantum number.
The structure of spontaneous decay of atoms in the vicinity of a surface is shown to be determined by spatial symmetries. The spontaneous-decay operator for a degenerate two level atom is derived, and with symmetry considerations the number of free parameters is reduced to two. Only the dimensionless and normalized inverse lifetimes b-parallel and b-perpendicular for a parallel and perpendicular dipole moment with respect to the surface, respectively, enter the expression for the relaxation operator for any atom near any surface. These two parameters incorporate the atom-surface-distance dependence of all Einstein coefficients for spontaneous decay, and all optical properties of the substrate material. It is shown that the specific features of spontaneous decay are mainly geometrical, and a consequence of symmetries of the vacuum radiation field, irrespective of the presence of the atom. With an example, it is shown how the parameters b-parallel and b-perpendicular can be calculated in a particular case. It is also pointed out that an explicit quantization of the radiation field can be avoided, even though the process of spontaneous emission is purely quantum mechanical.
The photon correlations of resonance fluorescence emitted by a degenerate two-level atom near a metal surface are studied. An intense nonmonochromatic optical laser drives a low-lying atomic transition, and the emitted fluorescence is detected by a photon counter. An expression for the spontaneous-decay operator is derived, and it appears that the various substates of the upper level have a different lifetime due to the presence of the surface, or equivalently, due to the loss of spherical symmetry. The temporal photon correlation function is then evaluated in terms of a photon-emission operator and the time-evolution operator for the atomic density matrix. The general theory is exemplified with a detailed elaboration of the jg=0\ensuremath{\rightarrow}je=1 transition, for which the two-photon correlation is obtained explicitly as a function of the inverse lifetime A(h), depending on the atom-surface distance h, the laser linewidth, the detuning from resonance, and the dipole-coupling strength with the external field.
Abstract : The photon correlations of resonance fluorescence emitted by a degenerate two-level atom near a metal surface are studied. An intense non monochromatic optical laser drives a low lying atomic transition, and the emitted fluorescence is detected by a photon counter. An expression for the spontaneous decay operator is derived, and it appears that the various substates of the upper level have a different lifetime due to the presence of the surface, or equivalently, due to the loss of spherical symmetry. The temporal photon correlation function is then evaluated in terms of a photon-emission operator and the time evolution operator for the atomic density matrix. The general theory is exemplified with a detailed elaboration of the j sub g = 0 yields j sub e = 1 transition, for which the two-photon correlation is obtained explicitly as a function of the lifetime A(h), depending on the atom surface distance h, the laser linewidth, the detuning from resonance, and the dipole-coupling strength with the external field. Keywords: Photon correlations; Resonance fluorescence; Atom near metal surface; Loss of spherical symmetry; Substates; Different lifetimes.
Quantum electrodynamics of an atom near a surface is a timely problem in current theoretical research. It appears, however, that a full dynamical theory, which includes both the time evolution of the atomic density operator and the details of the fluorescence radiation (temporal photon distribution) has never been formulated. In this paper the quantum theory of an atom near a perfect conductor is presented, and it is indicated how the formalism can be modified to account for more realistic optically active substrates. An expression is derived for the atomic spontaneous-decay Liouville operator from the Hamiltonian, which recovers the familiar results for the lifetimes and energy shifts. Furthermore, the emitted power is calculated as a function of time from the explicit expression for the radiation field. Comparison of the atomic-decay rates with the power of the emitted radiation shows the consistency of the theory, as far as the properties of the fluoresence are concerned. An unusual energy interference in the fluorescence, which is emitted by a multilevel atom, is predicted. Similarities and discrepancies with other theories are pointed out, and it is shown that especially the mirror theory has a very restricted applicability.
Abstract : In this Comment we discuss the general features of spontaneous decay of an atom which is close to the surface of a dielectric (or metal) layer, and this is compared to atomic decay near a four-wave mixing phase conjugator. It is pointed out that the decay or relaxation constants can be expressed entirely in terms of the classical Fresnel coefficients for reflection and transmission of a plane wave, independent of what the explicit forms of these coefficients are. For decay near a dielectric the relaxation constants can be measured directly by counting the number of fluorescent photons per unit of time, after excitation by a laser. For relaxation near a phase conjugator this procedure would require a spectral resolution in the photon detection, since there are two distinct contributions to the fluorescent yield of a two-state atom. The two possible decay mechanisms have different relaxation constants and produce radiation with different frequencies. Atomic relaxation, Near an interface, Emitted fluorescence, Classical fresnel coefficients, Phase conjugator, Four-wave mixing. (jes)