Spontaneous emission of a two-level atom with an arbitrarily polarized electric dipole in front of a flat dielectric surface

摘要

We investigate spontaneous emission of a two-level atom with an arbitrarilypolarized electric dipole in front of a flat dielectric surface. We treat thegeneral case where the atomic dipole matrix element is a complex vector, thatis, the atomic dipole can rotate with time in space. We calculate the rates ofspontaneous emission into evanescent and radiation modes and study the angulardensities of the rates in the space of wave vectors for the field modes. Weshow that, when the ellipticity of the atomic dipole is not zero, the angulardensity of the spontaneous emission rate of the atom may have different valuesfor modes with opposite in-plane wave vectors. We find that this asymmetry ofthe angular density of the spontaneous emission rate under central inversion inthe space of in-plane wave vectors is a result of spin-orbit coupling of lightand occurs when the ellipticity vector of the atomic dipole polarizationoverlaps with the ellipticity vector of the field mode polarization. Due to thefast decay of the field in the evanescent modes, the difference between therates of spontaneous emission into evanescent modes with opposite in-plane wavevectors decreases monotonically with increasing distance from the atom to theinterface. Due to the oscillatory behavior of the interference between theemitted and reflected fields, the difference between the rates of spontaneousemission into radiation modes with opposite in-plane wave vectors oscillateswith increasing distance from the atom to the interface. This difference can bepositive or negative, depending on the atom-interface distance, and is zero forthe zero distance.