Microwave two-photon spectroscopy of cesium Rydberg atoms

We present a two-photon microwave spectra of cesium Rydberg atoms in the room-temperature vapor cell. The three-level atom including a ground state 6 S 1/2 ( F = 4), an excited state 6 P 3/2 ( F ′ = 5) and Rydberg state consists of Rydberg electromagnetically induced transparency (Rydberg-EIT), that is employed to detect the microwave two-photon spectra. The microwave field with frequency ν DD = 11.42865 GHz couples the transition of Rydberg energy level |68 D 5/2 〉 → |69 D 5/2 〉, measured two-photon spectra display a rich of information including the microwave ac Stark shifts and two-photon Autler-Townes (AT) splitting. In the strong microwave field, the two-photon spectroscopy shows the state mixture between |68 D 5/2 〉 and |68 D 3/2 〉 Stark lines. The microwave two-photon spectra of the |69 S 1/2 〉 → |70 S 1/2 〉 transition coupled with frequency ν SS = 11.73503 GHz are also presented. The Floquet theory is employed to simulate the two-photon microwave spectra, showing the good agreement with the measurements. The work suggests the new method that may be used to investigate the multi-photon field-atom interaction and as an atom-based technique for precision field measurements.