“…Due to the presence of permanent dipole moments (PDM) in polar molecules, new phenomena emerges which are significantly different from the ones in absence of PDM. So far, there has been studies on the effects of PDMs on EIT [16,17], STIRAP [18,19], pulse propagation [20], higher harmonic generation [21], population inversion [22] and optical bistability [23]. In this work, we study the propagation of a weak probe pulse through a closed loop three level Λ system with PDMs in presence of a strong control field and a third field.…”