The Coherent Manipulation Of Spontaneous Emission

The coherent manipulation of spontaneous emission of a three-level A atom is studied by provoking the quantum regression theorem and the Fourier transform. It's revealed that for a realistic system, interference effects are obtained such as the suppression of the central line and inner sidebands and the narrowing of the outer sidebands. For this purpose, the spontaneous decay from an excited state to a metastable state is considered when the excited and metastable states are resonantly coupled to an auxiliary metastable state by a laser field and a microwave field, respectively. The spontaneous spectrum evolves from a five-peaked structure into a doublet of ultrasharp lines as the ratio of the laser field Rabi frequency to the microwave Rabi frequency is decreased.Bichromatic and trichromatic manipulation of spontaneous emission in a three-level system in A configuration is also investigated. The spontaneous emission spectrum is numerically calculated by using harmonic expansion and matrix inversion. Two characteristic features are shown. Firstly, the central resonance peak, which is absent in the case of monochromatic excitation, is recovered for the bichromatic or trichromatic excitation. Secondly, the selective elimination of the spectral lines is obtained by varying the amplitudes and phases of the trichromatic components. For the phase dependence, it is the sum of the relative phases of the two sideband components to the central component that plays a crucial role. The spontaneous emission spectrum is drastically modified once the sum phase is changed, but is kept unchanged regardless of the respective phases when the sum phase is fixed.