Spatial Deformation Mechnisim of Meta-Atom Coupling and Scaling

Abstract: Metasurfaces enable precise manipulation of light-matter interactions, and meta-atom coupling and scaling dominates their resonant properties and functional responses. Conventionally, coupled-mode theory (CMT), coupled dipole theory (CDT) and full-wave simulation are widely adopted to analyze such coupling effects. Nevertheless, CMT and CDT are essentially phenomenological theories. Although full-wave simulation delivers high calculation accuracy, it lacks physical insight and is generally regarded as a black-box method. Here, we combine transformation optics and perturbation theory to reveal that coupling and scaling fundamentally stems from the perturbation effect induced by spatial deformation. This establishes an intuitive and universal physical picture for the coupling mechanism. Based on the proposed principle, we demonstrate the anisotropic shift of grating resonant peaks, interpret the resonance frequency drift caused by coupling of the meta-atoms, and further clarify the tuning law of resonant frequency via geometric scaling of unit structures. Theoretical predictions show excellent consistency with full-wave simulation results in all three scenarios. Given the broad applicability transformation optics and perturbation theory, the established framework possesses favorable scalability and can be potentially extended to diverse research fields including photonics crystals, Bragg fibers, two-dimensional materials and crystalline optical properties.