Frequency modulation of Rydberg states by radio frequency electromagnetic fields
In this work, we demonstrate the generation of sidebands in electromagnetically induced transparency (EIT) signal due to frequency modulation of Rydberg states in $^{87}\text{Rb}$ thermal vapor. An oscillating radio-frequency (RF) electric field generated through a pair of parallel-placed copper plates leads to modulation of the Rydberg state by virtue of Stark effect where the frequency and strength of the sidebands quantify the RF electric field present. The variation of the strength of the EIT peak and the sidebands with RF voltage is observed to vary as a function of the Bessel function of modulation index. It provides an estimate of the atomic polarizability in the medium, which for $54S_{1/2}$ state, is found to be $(h)\cdot1.01\times10^8$ $\text{Hz/(V/cm)}^2$.