Enhanced electric field sensitivity of rf-dressed Rydberg dark states

Optical detection of Rydberg states using electromagnetically induced transparency (EIT) enables continuous measurement of electric fields in a confined geometry. In this paper, we demonstrate the formation of radio frequency (rf)-dressed EIT resonances in a thermal Rb vapour and show that such states exhibit enhanced sensitivity to dc electric fields compared to their bare counterparts. Fitting the corresponding EIT profile enables precise measurements of the dc field independent of laser frequency fluctuations. Our results suggest that space charges within the enclosed cell reduce electric field inhomogeneities within the interaction region.