Karl Heinz Drexhage

Spontaneous Emission Rate in the Presence of a Mirror

Recently it was shown experimentally that the decay time of fluorescence is influenced by a mirror[1–3]. It was decreased or increased depending on the distance from the mirror. Owing to the very low density of excited molecules in these experiments, the observed phenomenon must be ascribed to an influence of the mirror on the rate of spontaneous emission of each excited molecule alone. A theoretical treatment is given which is based on the radiation of a classical oscillator, and it is applied to the actual experimental situations of a metal mirror, a boundary between media of different refractive indices, and a system of two or more parallel mirrors. The strong birefringence of the environment of the fluorescing molecules and competing nonradiative processes is taken into account in order to permit a quantitative comparison with the experimental data.