Transmission-type coding metasurface for spatially tailored Rydberg-atom microwave sensing

Rydberg-atom microwave electrometry offers SI traceability, low perturbation, and broad frequency tunability, but weak microwave coupling within the light-atom interaction region can limit the detectable spectral response. Here, a 4-bit transmission-type coding metasurface is introduced as the microwave-field control component of a hybrid sensing architecture for Rydberg-atom microwave electrometry. Rather than simply increasing the local microwave intensity, the metasurface manipulates the transmitted microwave wavefront to generate different spatial field distributions and improve the spatial overlap between the microwave field and the optically interrogated atomic sensing volume. Using the same sixteen-state coding library, three field-control configurations are realized at 15.5 GHz: transverse extended-depth enhancement, axial near-field enhancement, and four-channel near-field beam splitting. The average power-density gains within the light-atom interaction regions are 13.41, 17.15, and 8.38 dB, respectively. These results demonstrate that a common coding library can provide versatile microwave-field distributions and spatial sampling functions through different spatial arrangements, offering a flexible approach for different Rydberg-atom interrogation geometries.