3-Photon Rydberg-Atom Electrometry with High Sensitivity

We demonstrate high sensitivity, all optical radio-frequency electrometry using Rydberg atoms by employing a colinear three-photon excitation scheme in a cesium (Cs) vapor cell at room temperature. By using a wavevector matching condition unique to Cs, our setup reduces residual Doppler broadening of the probe laser electromagnetically induced absorption to sub-200 kHz linewidths. The narrow linewidth allows for the extension of the self-calibrated Autler-Townes sensing regime. We report our latest sensitivity measurements after improving laser linewidths, increasing laser power, and implementing more sensitive probe laser detection. Density matrix calculations were used to optimize the parameters. The enhancements have led to the successful detection of radio-frequency Rabi frequencies of 2π × 69 kHz using a 480-kHz bandwidth at 10.7 GHz. The results from our experiment show over an eightfold enhancement compared to our previously reported findings¹. Our measurements show the capability of detecting time-dependent signals suitable for radar and communications with high sensitivity. Prospects for further enhancing the sensitivity will be described.