Interference Between Competing Pathways in the Interaction of Three-Level Ladder Atoms and Radiation

In this paper we explore the physical origin of the transparency induced in absorbing three-level cascade atoms by the simultaneous interplay of two coherent beams of light. By utilizing the scattering technique we offer what we believe is a very convincing physical evidence for the existence, or for the absence, of quantum interference effects in the Autler-Townes (AT) and Electromagnetically Induced Transparency (EIT) phenomena.