Rydberg atomic sensing and laser stabilization using an inverted ladder excitation scheme

We present a Cesium Rydberg atom excitation scheme using a probe transition of 6S_1/2 →7P_1/2 (λ_p = 459 nm) and coupling transition of 7_1/2 →nD_3/2 (λ_c >1038 nm) for microwave and mm-wave electric field sensing. With development of compact and vibration robust systems in mind, we use this inverted ladder scheme (λ_p < λ_c) as an alternative to schemes that use the D₁ and D₂ probe laser transitions and 494 nm and 510 nm green light coupling laser transitions which can require sophisticated laser architectures as a result of second harmonic generation. We demonstrate 459 nm probe laser stabilization to the F=3 to F=4 hyperfine transitions in a saturated absorption spectroscopy configuration, and demonstrate laser stabilization of the 1038 nm coupling laser to electromagnetically induced transparency in a counter-propagating probe and coupling laser configuration. Under stabilization, Allan deviations of less than 200 kHz for τ < 50 s are achieved for both the probe and coupling lasers. Finally, we conduct proof-of-concept experiments to validate Autler-Townes splitting of the nD_3/2 →(n + 1)P_1/2 and nD_3/2 →(n−2)F_5/2 neighboring Rydberg transitions in the presence of on-resonance mm-wave field.