Resonance‐Mode Manipulation Enabled by Low‐Symmetry in Spoof Localized Surface Plasmon Structures

ABSTRACT

Resonance‐mode manipulation is a fundamental and critical issue in electromagnetic science, underpinning diverse functions including energy localization, wave modulation, nonlinear interactions, and information processing across frequencies from microwaves to optics. Here, we propose to manipulate the mode resonance and coupling based on spoof localized surface plasmon (SLSP) on metallic spiral structures (MSS) with low‐symmetry, which are composed of four spiral arms with two different lengths. By extending group representation theory to low‐symmetry configurations and introducing the concept of current order, the resonance and coupling behaviors can be analytically predicted, showing excellent agreement with numerical simulations and measured results. Two distinct magnetic dipole modes are discovered, supported by the first‐order and second‐order current distributions, respectively. Tuning the length difference between spiral arms enables lower resonance frequencies and greater flexibility in coupling control. These findings help understand mode manipulation by symmetry in electromagnetic metamaterials, enrich the toolbox for resonance and coupling engineering, and open new avenues to develop advanced resonance devices.