Frequency modulation of Rydberg states by radio frequency electromagnetic fields

This study demonstrates the frequency modulation of Rydberg states in 87Rb thermal vapor leading to the production of sidebands in electromagnetically induced transparency (EIT) signal. The modulation is provided externally through radio-frequency (RF) electric fields from a parallel-plate capacitor. The modified EIT signal is detected via the conventional lock-in amplified EIT setup. We assess the strengths of the peaks in the modulated EIT spectrum and compare them to a mathematical model based on Floquet theory. The relationship between the strength of the EIT peaks and the RF voltage is identified as a function of the Bessel function of the modulation index.