Correlations between photons emitted by an atom in a laser field and near a metal surface are studied. With polarisation-dependent detection it is feasible to select photons which are emitted in a specific transition between degenerate substates. Both the Einstein coefficient for spontaneous decay of a particular excited substate and its branching towards the various ground states depend on the distance between the atom and the surface. A combination of these notions to design a geometry for the correlated detection of polarised photons is employed, in order to predict a strong dependence of the correlation functions on the atom-surface distance. In general, an enhancement of the correlations between emitted photons due to the presence of the metal surface is found if the atom-surface distance is (roughly) less than 20% of the wavelength of the fluorescence radiation. In particular the correlations between circularly polarised photons with the same helicity are modified dramatically, and the correlation time tends to infinity if the atom approaches the surface. It is pointed out how the different photon correlations can be understood from a simple interpretation of transition diagrams.
Correlations between photons emitted by an atom in a laser field and near a metal surface are studied. With polarisation-dependent detection it is feasible to select photons which are emitted in a specific transition between degenerate substates. Both the Einstein coefficient for spontaneous decay of a particular excited substate and its branching towards the various ground states depend on the distance between the atom and the surface. A combination of these notions to design a geometry for the correlated detection of polarised photons is employed, in order to predict a strong dependence of the correlation functions on the atom-surface distance. In general, an enhancement of the correlations between emitted photons due to the presence of the metal surface is found if the atom-surface distance is (roughly) less than 20% of the wavelength of the fluorescence radiation. In particular the correlations between circularly polarised photons with the same helicity are modified dramatically, and the correlation time tends to infinity if the atom approaches the surface. It is pointed out how the different photon correlations can be understood from a simple interpretation of transition diagrams.
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.
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.
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 : 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.
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}jeme〉 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.
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.