EIT line shape in an open and partially closed multilevel V-type system

A detail theoretical analysis based on density matrix formulation is carried out to study the electromagnetically induced transparency in a multilevel open V-type system. The density matrix equations are solved numerically for both the Doppler-free and Doppler-broadened medium. We get two coherent electromagnetically induced transparency (EIT) peaks of sub-natural line width and five saturation peaks of sub-Doppler line width. The effect of decoherence on the EIT peak is studied using the theoretical model. A comparative study of the EIT line shape for open and closed V-type system has been done using the theoretical results. In our experiment, we have observed one EIT peak and four saturation peaks in an open V-type system corresponding to the D2 transition of 85Rb atoms and the EIT peak gets enhanced for partially closed V-type system compared to the open system. The dependence of height and width of the EIT line shape for different pump power values is also observed. The experimental observations are simulated numerically with a good agreement. We have also reported a noticeable change in the contrast of the EIT resonance due to the tuning of the pump laser frequency over the entire probe Doppler profile.