Amplification without inversion in Y-type four-level scheme

In this paper, we have investigated amplification without inversion (AWI) in a Y-type four-level atomic system. We have considered the effect of control fields’ amplitude, their phases and detuning between atomic transition and applied fields, on imaginary part of optical susceptibility. It has been shown that, with proper setting of control fields’ amplitude, while setting phases to zero, we can obtain gain and with proper setting of phase difference of control and probe fields; we can obtain considerable gain in resonant wavelength.