Gain components in the Autler-Townes doublet from quantum interferences indecay channels - art. no. 013807

We consider nondegenerate pump-probe spectroscopy of V systems under condit ions such that interference among decay channels is important. We demonstra te how this interference can result in new gain features instead of the usu al absorption features. We relate this gain to the existence of a new vacuu m induced quasi-trapped-state. We further show how this also results in a l arge refractive index with low absorption.