Role of dressed-state interference in electromagnetically induced transparency

Electromagnetically induced transparency (EIT) in three-level systems uses a strong control laser on one transition to modify the absorption of a weak probe laser on a second transition. The control laser creates dressed states whose decay pathways show interference. We study the role of dressed-state interference in causing EIT in the three types of three-level systems-lambda (Λ), ladder (Ξ), and vee (V). In order to get realistic values for the linewidths of the energy levels involved, we consider appropriate hyperfine levels of 87Rb. For such realistic systems, we find that dressed-state interference causes probe absorption-given by the imaginary part of the susceptibility-to go to zero in a Λ system, but plays a negligible role in Ξ and V systems.