Population inversion and absorption spectrum of a V-typethree-level atom driven by coherent and stochastic fields

Abstract

The steady-state populations and the absorption spectrum of a V-typethree-level atom driven by a strong coherent field and a weak stochasticonesimultaneously are investigated. The population inversion in bare-stateand dressed-state bases can happen significantly due to the effect of thestochastic field. A relation between the level gap of both atomic excitedstatesand the Rabi frequency is found to decide in which excited statethe population is larger than in another one for the same frequencydetuning δ between the coherent and the stochastic fields.The line profiles of the absorption spectrum are strongly dependent on thefrequency detuning δ. Different lineshapes such as a sharpemissionpeak (gain), an absorption peak or a dispersion-like peak canbe exhibitedat thelinecentre for different δ. Asymmetrical spectral features and linenarrowing can be reached by adjusting δ and theRabi frequency.Probe gain in sidebands can occur due to the unbalanced populationdistributionin dressed states.