Effect of spontaneously generated coherence on absorption and dispersion in probe laser

Abstract

A theoretical investigation is carried into the effect of spontaneously generated coherence on absorption and dispersion in probe laser of Y-type atom system. It is found that the electromagnetically induce transparency window in the system narrows gradually as the spontaneously generated coherence intensifies. Moreover, the anomalous dispersion appears and the absorption changes from negative value to positive valve at resonance. At the same time, the absorption is zero or negative near resonance when the relative strength of the coupling field and pump field are different, and the atomic medium shows positive absorption when the two fields are exattly or nearly equal and close.