Localized Ion Irradiation Enables Topography‐Free High‐Tc Superconducting Metamaterials

Superconducting metamaterials promise ultra‐low‐loss photonic platforms for quantum technologies, yet their scalability has long been constrained by fabrication itself. Conventional patterning methods rely on physical material removal, inevitably introducing edge damage, oxygen loss, and structural inhomogeneity that degrade the superconducting properties they are intended to exploit. Here, we overcome this challenge by introducing a topography‐free fabrication strategy based on localized oxygen ion irradiation that patterns superconducting YBa 2 Cu 3 O 7 without etching the film. Instead of removing material, ion irradiation selectively suppresses superconductivity through controlled lattice disorder, creating high‐contrast functional architectures while preserving the surrounding pristine superconducting film. Using this approach, we realize 50 and 200 nm terahertz asymmetric split‐ring metamaterials exhibiting pronounced Fano and dipole resonances with temperature‐controlled frequency tuning of upto 220 GHz. The thinner superconducting films display enhanced tunability arising from increased kinetic inductance, while optical pump‐terahertz probe spectroscopy reveals ultrafast resonance modulation approaching 76%, confirming efficient photoinduced Cooper‐pair dynamics. Compared with representative wet‐etched superconducting metamaterials, the ion‐defined structures exhibit improved resonance performance while eliminating the need for subtractive processing. These results establish localized ion irradiation as a scalable route for defining superconducting photonic circuits, opening new opportunities for high‐T c superinductors, fluxonium architectures, and integrated quantum and terahertz technologies.