Microwave field sensor based on the cold cesium Rydberg three-photon electromagnetically induced spectroscopy

We present the electromagnetically induced transparency (EIT) spectra of cold Rydberg four-level cascade atoms consisting of the 6 S 1/2 → 6 P 3/2 → 7 S 1/2 → 60 P 3/2 scheme. A coupling laser drives the Rydberg transition, a dressing laser couples two intermediate levels, and a weak probe laser probes the EIT signal. We numerically solve the Bloch equations and investigate the dependence of the probe transmission rate signal on the coupling and dressing lasers. We found that the probe transmission rate can display the EIT or electromagnetically induced absorption (EIA) profile, depending on the coupling and dressing laser Rabi frequency. When we increase the coupling laser Rabi frequency and keep the probe and dressing laser Rabi frequency fixed, flipping of EIA to EIT spectrum occurs at the critical coupling Rabi frequency. When we apply a microwave field coupling the transition of 60 P 3/2 → 61 S 1/2 , the EIT spectrum forms the AutlerTownes (AT) splitting, which is employed to measure microwave field. The measurement sensitivity in theory can be 1.52×10 -2 nVcm -1 Hz -1/2 at the EIA-EIT flapping point.