Investigation of Five-Level Excitation Schemes for Rydberg Atom-based Radio Frequency Field Metrology

Electromagnetically-induced transparency (EIT) techniques have been used to successfully detect and characterize radio frequency (RF) fields. This approach typically uses a four-level excitation scheme, which include a probe laser (levels | 1 > --> | 2 >), a coupling laser to Rydberg states (| 2 > --> | 3 >), and an RF source to couple two Rydberg states (| 3 > --> | 4 >). In this talk we explore five-level excitation schemes. In the first scheme we add a fifth level, which is another Rydberg state, that is coupled by a second RF source (| 4 > --> | 5 >). The second scheme is a five-level ``Y'' scheme, which includes two ground state transitions, | 1 > --> | 2 > (5S_{1 / 2 , F = 3} --> 5P_{3 / 2 , F = 3}), and | 3 > --> | 2 > (5S_{1 / 2 , F = 2} --> 5P_{3 / 2 , F = 3}). A coupling laser generates Rydberg states (| 2 > --> | 4 >), and RF couples two Rydberg states (| 4 > --> | 5 >). We show experimental results for the two different 5-level schemes and discuss novel features observed in the spectra of these five-level schemes. We describe their dependence on frequency detuning and power variations, and compare with theoretical models.