Semiclassical description of radiative decay in a colored vacuum

Recently, there has been considerable interest in atoms confined to optical cavities or embedded within photonic band-gap materials, where the spectrum of vacuum fluctuations is modified. As a first step in extending traditional semiclassical methods into this regime, the present paper describes a semiclassical, density-matrix methodology for treating radiative processes in a low-Q cavity. This semiclassical approach is tested by comparing its predictions to the optical cavity experiments of Heinzen and Feld [Phys. Rev. Lett. 59, 2623 (1987)] and by calculating transient-nutation decay in free space induced by a broadband laser. The methodology is then used to examine transient nutation in a low-Q optical cavity, where it is found that the detuning between the atomic and cavity resonances has a significant effect on the transient nutation's decay rate