Role of selective excitation of dressed populations in lasing without inversion

Abstract

Exemplifying the three-level systems in the V configuration, we investigate the role of selective excitation of dressed populations in lasing without inversion. Incoherent driving field transfers population from either of the dressed states to excited state when the level spacing between dressed states produced by the coherent field is much larger than the spectral width of the incoherent driving field. With atomic decay pathways，unidirectional channel of population transfer is formed and selective excitation of dressed populations is established. Employing selective excitation of dressed populations，three severe limits are relaxed. First，it is no longer required that the decay rate of the low-frequency driving transition is larger than that of high-frequency laser transition. Second，the threshold for incoherent driving rate is remarkably lowered. Third，linear gain of the laser without inversion is no longer inversely proportional to the coherent driving field intensity, and the gain is significantly enhanced.