Gain without population inversion in V-type systems driven by a frequency-modulated field

Abstract

We obtain the gain of the probe field at multiple frequencies in a closed three-level V-type system using a frequency-modulated pump field. There is no associated population inversion among the atomic states of the probe transition. We describe both the steady-state and transient dynamics of this system. Under suitable conditions, the system exhibits a large gain simultaneously at a series of frequencies far removed from resonance. Moreover, the system can be tailored to exhibit multiple frequency regimes where the probe experiences anomalous dispersion accompanied by negligible gain or absorption over a large bandwidth, a desirable feature for obtaining superluminal propagation of pulses with negligible distortion.