Electromagnetically induced amplification via counter-rotating-wave terms in a three-level Λ-type system

Abstract

We report the remarkable phenomena caused by high-order interaction of counter-rotating-wave terms in a three-level Λ-type system coupled with two laser fields. With the low-order interaction of the rotating-wave terms, transparency induced by Autler−Townes splitting is obtained. When the high-order interaction of the counter-rotating-wave terms is considered, some sideband peaks show up and the probe field is amplified without population inversion. The stronger the coupling, the larger the amplification. The gain of probe photons comes mainly from the loss of the control field through a one-photon or two-photon process.