Control of optical properties of materials by atomic coherence and quantum interference effects

We investigate the spontaneous emission spectrum of a three-level atom coherently driven by a microwave field. The microwave excitation establishes a coherent link between the bottom two levels, and as a consequence induces the quantum interference of previously independent decay pathways. As the decay pathways differ from one another by an odd number of stimulated emission processes, the spontaneous emission spectrum acquires a dependence on the phase of the excitation field, a feature that is absent in other resonance fluorescence phenomena