Gain without population inversion in a yoked superfluorescence scheme

Abstract

We consider a medium composed of three-level (cascade scheme) atoms prepared with coherence between the upper and the ground states (a yoked superfluorescence system). We obtain an analytical solution for propagation of seed pulses which are resonant with the upper and lower transitions for arbitrary level populations and pulse shapes. We find that if the initial coherence is large enough and the intermediate level is populated the system can have gain without population inversion. Coherence can also yield gain suppression in the inverted medium. We obtain conditions for the gain in terms of level populations and coherence.