Sensitivity Measurements of UHF-Band Electric Fields with Electromagnetically-Induced Transparency and Heterodyne Detection

We present results on Rydberg atom-based electric field sensing in the ultra high frequency (UHF) radio band. Like other frequency bands of radio and microwave radiation, UHF signals can be detected with atom-based field sensing by resonantly driving Rydberg-Rydberg transitions and observing the atomic response. In this work, we utilize a three-photon excitation scheme to excite rubidium-87 atoms in a vapor cell to Rydberg F-states. At these states, UHF signals can resonantly drive nF → nG transitions and perturb the absorption coefficient of the atomic vapor. The magnitude of the UHF signals is then determined by monitoring the absorption of the probe laser through the vapor cell. We measure applied signal fields with heterodyne detection, which allows for enhanced detection of weak fields. The sensor's resonant frequency and sensitivity are a function of the principal quantum number n of the nF → nG transition; for n = 45, we report a sensitivity of 3.9 μV/(m√Hz) at a signal frequency of 899 MHz.