Microwave or radio-frequency controlled electromagnetically induced transparency (EIT) and related dispersion spectra in a pump-probe lasers driven multi-level [formula omitted]-type system of [formula omitted] atom

Abstract

The optical responses of a pump-probe lasers driven six-level cascade (Ξ)-type system to the probe field are studied in the present work. The six-level system considered to be formed by the hyperfine energy levels of 5S12, 5P12 and 7S12 states of 87Rb atom. The main feature that makes the present light-atom interaction scheme different from the other routinely studied Ξ-type systems is the coupling of magnetic dipole allowed hyperfine ground levels by the magnetic field component of a microwave (MW) or radio-frequency (RF) field and the use of it as a control field. Probe absorption and dispersion profiles are simulated by numerically solving the corresponding optical Bloch equations (OBEs). Effects of the MW or RF field on the electromagnetically induced transparency (EIT) as well as probe absorption and related dispersion signals are examined under strong pump and different probe strength conditions. Group index (ng) of the medium is also evaluated and the effect of the MW or RF field on ng is explored. It has been found that the MW or RF field, working as a control field in the medium facilitates the enhancement of the overall absorption of the probe field in weak and moderate probe strength limits for stationary as well as for moving atoms. At higher probe strength, the MW or RF field contributes in the subluminal probe propagation through the stationary atomic medium along with a non-vanishing probe absorption at the line center.