Quantum interference coherently driven systems

V. Quantum Interference Effects in Coherently Driven Systems... 

V. QUANTUM INTERFERENCE EFFECTS IN COHERENTLY DRIVEN SYSTEMS... 

The discussion, presented in Section IV, has been concentrated on analysis of the effect of quantum interference on spontaneous emission in a V-type three-level atom. With the specific examples we have demonstrated that spontaneous emission can be controlled and even suppressed by quantum interference. In this section, we extend the analysis to the case of coherently driven systems. We will present simple models for quantum interference in which atomic systems are composed of two coupled dipole subsystems. In particular, we consider interference effects in coherently driven V and A-type three-level atoms. Each of the three systems is represented by two dipole moments, p, and p2, interacting through the vacuum field. 

Another area of interest in quantum interference effects, which has been studied extensively, is the response of a V-type three-level atom to a coherent laser field directly coupled to the decaying transitions. This was studied by Cardimona et al. [36], who found that the system can be driven into a trapping state in which quantum interference prevents any fluorescence from the excited levels, regardless of the intensity of the driving laser. Similar predictions have been reported by Zhou and Swain [5], who have shown that ultrasharp spectral lines can be predicted in the fluorescence spectrum when the dipole moments of the atomic transitions are nearly parallel and the fluorescence can be completely quenched when the dipole moments are exactly parallel. 

The three-level saturation spectroscopy of A- and V-level configurations flourished in the subsequent years and led to the discovery of munerous new effects, such as coherent population trapping (Arimondo 1996), electromagnetically induced transparency (Harris 1997), and lasing without population inversion (Kocharovskaya 1992). These effects are beyond the scope of the present book. The control of quantum coherence and interference in laser-driven three-level systems has been treated in detail in the excellent reviews cited above. 

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