Over the last two decades the atomic coherence and quantum interference were extensively used in high resolution laser spectroscopy. As a matter of fact a new branch of spectroscopy, termed as coherent optical spectra has been emerged to incorporate phase dependent effects on the spectral lines, as well as various nonlinear absorption processes. Apart from spectroscopic point of view, the coherency effects for some fascinating counter intuitive quantum optical phenomena, regarding wave propagation and hence on the control of optical properties of the medium is an active research subject. This...