Optical pumping effects on high-contrast Rydberg electromagnetically induced transparency

We discuss the interplay between high-contrast Rydberg-state electromagnetically induced transparency (EIT) and optical pumping (OP) in a thermal [Formula: see text]Rb medium. By pumping the population to one single hyperfine state, we can enhance the interaction strength and, in principle, amplify the EIT peak. According to the measurements, the EIT peak height can be improved by a factor of two or reduced by one order of magnitude, and linewidth was slightly narrowed by the pumping effect. The EIT feature is predicted quantitatively using a Doppler-free non-perturbation numerical calculation. In both simulations and measurements, Rydberg-EIT enhancement through OP is dependent on the intensity of the probe field and the optical density. Our work clarifies the underlying mechanisms of optical pumping, making relevant studies useful in developing Rydberg-based electrometry.