Spontaneous emission from an atom inside a dielectric sphere

A quantum mechanical treatment for the spontaneous emission from a two-level atom inside a dielectric sphere with a continuum of electric field modes is presented. The analytical expressions for the spontaneous emission rates obtained by Chew [J. Chem. Phys. 87 (1987) 1355] in a classical treatment for an oscillating dipole are shown to be contained in our theory. A delay-differential equation, which shows how multiple reflections off the dielectric sphere surface alter the emission of the atom in a multimode lossy cavity, is derived in a nonperturbative fashion. The numerical solution to this equation shows that vacuum-field Rabi oscillations in the case of a spherical cavity are rather strong as compared to the case of a planar Fabry-Perot cavity. The conditions for vacuum-Rabi oscillations and the enhancement of the spontaneous emission rate in the single-mode regime of a spherical cavity are discussed. (C) 2000 Published by Elsevier Science B.V. All rights reserved.