Optical properties of four level medium via spontaneously generated coherence

In this paper, we investigated phase effect of spontaneously generated coherence (SGC) on transient and steady state behavior of weak probe field in Y-type four-level atomic system in the presence of two coupling fields. It is found that the probe absorption can be vanished and converted to probe gain in the absence of population inversion. Also it is shown that relative phase between coupling fields can influence the probe gain. Moreover, it is investigated that dispersion slope can be changed from positive to negative via spontaneously generated coherence.