title: Dressed-atom multiphoton analysis of anomalous electromagnetically induced absorption.
abstract: A method to interpret probe spectra of driven degenerate atomic systems is discussed. The dressed-atom multiphoton spectroscopy (DAMS) is based on a dressing of the atomic system with the strong coupling field, followed by a perturbative treatment of the probe field interaction. As an example, we apply the DAMS to provide a clear interpretation for anomalous electromagnetically induced absorption (EIA), which cannot be explained by spontaneous transfer of coherence. We show that anomalous EIA arises from quantum interference among competing two-photon transitions and explain the different dependences on the coupling field strength observed for various angular momentum setups.
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany.
authors.forename: Hsiang-Shun
authors.initials: HS
authors.lastname: Chou
authors.forename: Jörg
authors.initials: J
authors.lastname: Evers