Reconfigurable nonreciprocal isolation enabled by nonlinear spoof surface plasmons

Spoof plasmonics, with unique quasi-optical and quasi-electrical properties, have emerged as a promising route toward compact, high-speed, and CMOS-compatible devices for next-generation integrated systems. A key requirement for advancing such circuits is nonreciprocal functionality, which enables signal routing, source protection, and suppression of backscattering. Conventional nonreciprocal schemes, however, typically rely on bulky magnetic components that lack tunability and remain incompatible with compact integrated platforms. Here, we demonstrate a nonlinear spoof plasmonic waveguide composed of a corrugated spoof plasmonic surface integrated with nonlinear circuit elements, enabling reconfigurable nonreciprocal isolation through strong field confinement, engineered dispersion, and nonlinear interactions. Efficient three-wave mixing processes dynamically break reciprocity without magnetic bias. Back-propagating waves undergo monotonic attenuation under a special phase-matching condition enabled by multi-mode spoof plasmonic dispersion, while forward-propagating waves remain unaffected. Theoretical and experimental results demonstrate an isolation ratio of 10 dB with an insertion loss of −3 dB over a bandwidth of 270 MHz, achieved within a compact device length of 210 mm (approximately 1.75 λ 0 ). Dynamic tunability is further enabled by controlling the pump amplitude and frequency. These results establish nonlinear spoof plasmonic waveguides as a compact and reconfigurable platform for nonreciprocal isolators, with strong potential for applications in wireless communication, radar systems, and ultrahigh-speed integrated circuits.