Field Enhancement for Sensitivity Improvement of a Room-Temperature Rydberg-Atom Receiver

This paper presents a microwave cavity for sensitivity enhancement in room-temperature Rydberg atom electric field sensors. It can be shown theoretically that without enhancement, such sensors currently do not compete with conventional low-noise amplifier based receivers. We designed a 15 GHz resonator for a specific set of transitions in Rubidium atoms. Owing to its high Q and finesse, the resonator enhances the electric field magnitude sensed by the atoms by a factor F with respect to an external field coupled through an antenna. The resonator is designed to fit a 4 mm × 4 mm × 25 mm fused silica vapor cell. The simulated and measured Q-factors are 1900 and 1100, respectively, which corresponds with field enhancement factors of 20 and 14, respectively. The resonator is mechanically tunable over 216 MHz to ensure overlap with the atomic resonance.