Exploring the close analogy between classical electrodynamics and quantum electrodynamics, we have developed a general algorithm to calculate the spontaneous emission rate and the spontaneous emission factor in a microcavity of arbitrary geometry. Both the emission spectrum of the light source and the decay of the electromagnetic modes are taken into account in our model. Assuming a Lorentzian line shape for the emission spectrum, we apply our algorithm to calculate the spontaneous emission rate and the spontaneous emission factor in a dielectric microdisk cavity. We find that the spontaneous emission characteristics in the microdisk are greatly modified by the whispering gallery modes. The influence of the spectral linewidth of the light source on the spontaneous emission rate and the spontaneous emission factor is also discussed.

• Received 6 April 1999

DOI:https://doi.org/10.1103/PhysRevA.61.033808