Optimized T-shaped resonator via local enhancement model integration within a cell for enhanced Rydberg-atom receiver sensing.

Rydberg atom with resonators is regarded as promising atomic receivers to surpass conventional receivers' sensitivity. However, previous research has presented diverse open resonator structures, focusing on design yet lacking in theoretical guidance. Here we bridge this gap by elucidating the fundamental principles of local enhancement in open resonators, which guides us to adopt positive countermeasures aimed at maximizing the electric-field local enhancement ability and avoid blindly modifications. To overcome limitations of injection-type cylindrical resonators, which require external antennas and lack mobility, we propose an enclosed T-shaped resonator (TSR) integrated within a vapor cell for direct C-band coupling. Simulations show that the enhancement factor rises from 27 times of the basic parallel-plate resonator (PPR) to 57 times of the TSR at the same resonant frequency. An experimental validation was performed with an TSR. The TSR has 32.5 dB at 7.83 GHz electric-field local enhancement ability and an electrical size of 0.18 λ.