Observation of frequency diffraction management in spoof plasmonic waveguides

The engineering of electromagnetic waves in rf driving platforms is advancing rapidly, driven by advancements in topological photonics and waveguide technologies. However, challenges remain in achieving precise control over frequency diffraction and mode coupling in practical applications. Our work addresses these challenges by introducing an approach that incorporates a voltage-controlled, time-dependent varactor diode within a microwave spoof plasmonic waveguide. By employing periodic voltage modulations through square, sinusoidal, and sawtooth waveforms, we explore their distinct effects on discrete frequency diffraction, sideband suppression, and directional nondiffraction frequency shifts. Our findings demonstrate the efficacy of extended coupled mode equations, which include higher-order coupling terms, in facilitating harmonic control over electromagnetic spectra. Our research highlights potential applications in communication systems and signal processing technologies, paving the way for enhanced manipulation of electromagnetic waves in future integrated photonic devices. © 2025 American Physical Society.