A detailed study of the quantum coherent and saturating resonances using the hyperfine lines of rubidium

We have studied both experimentally and theoretically the V-type system in the hyperfine structure of the D1 and D2 lines of rubidium with co-propagating pump-probe laser fields. The experimental observation in the V-type system shows the high contrast EIT peak along with the saturation peaks in the probe Doppler profile. A velocity dependent analysis regarding the formations and frequency positions of the observed resonances has been done. The dependence of the EIT line shape on the variation of the pump laser intensity and detuning has been investigated. It is observed that the EIT resonance disappears for a pump power when it is less than the probe power and the saturating effects dominate over the coherence effects in the system. By properly tuning the pump laser, a perfectly symmetric EIT peak with high contrast is obtained at the center of the probe Doppler profile, while the strong saturating resonances get eliminated. A theoretical model based on the density matrix formulation has been presented corresponding to a five-level V-configuration. This model helps us to interpret the experimental observation theoretically.