Asymmetrical spectra due to atomic coherence of neighboring excited levels

In this paper, we propose to use two five-level systems to analyze asymmetrical transmitted spectra of probe field in traditional three-level Λ-type and ladder-type systems for electromagnetically induced transparency (EIT) and photonic band-gap in atoms with a strong coupling field. The five-level systems are constructed by choosing two additional levels adjoining to one of the upper or middle levels in a three-level Λ-type and ladder-type systems. Due to inhibited transition of the coupling laser to one of the two chosen levels, the asymmetrical absorptions at dressed states are obtained to be consistent with experimental observation in the original three-level systems.