Absorption profile of a three- Ievel ladder atomic system with incoherent PumPing

We have studied the effects of adding an incoherent population pumping on the absorption and dispersion profile of a driven three- level ladder system. Two coherent fields are assumed to drive our system, a coupling field on the upper transition and a probe field on the lower transition. The absorption profile of such a system with no incoherent pumping is well known. It consists of two symmetric (asymmetric) Autler- Townes peaks for resonant (off- resonant) coupling field We have found that applying an additional incoherent pumping field would work first to merge the two peaks into a central weak absorption line and then to drive the system to a state of electromagnetically induced transparency (EIT). We have found differences in the details of this effect when the pumping field is applied to the upper or to the lower atomic transition, in the latter case the transition of the system to the (EIT) state takes place very rapidly as compared to the former case. In the second case ancl for an off - resonant coupling field and fast upper transition relaxation, we have noticed an interesting effect manifested in the fact that the incoherent pumping field would shift the absorbed energy from the larger to the smaller absorption peak resulting in a non - central weak absorption line befbre reaching the ultimate (ElT) state