Superconducting circuits require high-speed, low-heat-load data transmission across temperature zones. Cryogenic electro-optic (EO) modulators with optical fiber links offer a superior solution. Conventional metallic electrodes suffer from severe ohmic loss, but superconducting electrodes exhibit near-zero resistance at cryogenic temperatures, which allows ultra-long traveling-wave electrodes that reduce half-wave voltage without sacrificing bandwidth.

We demonstrate a high-performance, scalable bent superconducting asymmetric coplanar waveguide (ACPW) on lithium niobate. The asymmetric gap enhances the central electric field by ~90%, improving modulation efficiency. A circular bend extends the interaction length within a limited chip area. To suppress bend-induced parasitic resonances, we integrate cross-line dielectric bridges. Its low curing temperature (95°C) prevents degradation of the Nb thin films, ensuring structural stability.

DC characterization shows a superconducting transition at 7.8 K with a narrow width of 0.03 K. High-frequency measurements at 4.2 K confirm the bridges mitigate parasitic resonances, improving the 3-dB bandwidth from 9 GHz to 59 GHz. This work provides a reliable material platform for next-generation high-speed cryogenic EO modulators.