In this paper we theoretically investigate the behavior of a two-level atom in a lossless cavity driven by an external field. Using classical electrodynamics to describe the external field while quantizing the cavity field, we find that the cavity field is excited to a coherent state whose amplitude is equal to that of the external field, but shifted 180° in phase. This results in the disappearance of the atomic resonance fluorescence (i.e., the atom stops interacting with the fields). When we quantize the external field the effect persists. A fully quantized dressed-state approach provides some helpful insight and a nice analogy to another problem in which the resonance fluorescence vanishes.

• Received 19 July 1991

DOI:https://doi.org/10.1103/PhysRevA.45.1793