Metasurface design using multiple meta-atoms as fundamental elements: a review

Abstract

Metasurfaces have emerged as a transformative platform that offers unprecedented capabilities for tailoring the amplitude, phase, and polarization of light with ultrathin planar structures. Their compact device footprint, functional versatility, and compatibility with scalable nanofabrication techniques have positioned them at the forefront of photonic research and technologies. Conventional metasurface designs rely on a single meta-atom per unit cell, selected from a predefined library to achieve a desired optical response. Although effective, this approach inherently lacks sufficient design degrees of freedom (DOFs), thereby constraining the achievable device functionalities. Recent developments have introduced metasurfaces that incorporate multiple meta-atoms within each supercell, dramatically expanding the available DOFs and enabling more sophisticated optical responses. This architectural shift has catalyzed rapid progress across a broad spectrum of applications, including imaging, beam steering, displays, and sensing. This review focuses on metasurfaces composed of multiple meta-atoms within a supercell and classifies their development into two distinct paradigms: local supercell architectures that enhance the DOFs of optical responses through interference, and nonlocal supercells based on quasi-bound states in the continuum (quasi-BICs) that leverage long-range modal coupling to achieve high quality factors and enhanced wavefront control. We summarize recent advances in multi-element metasurface design, examine the physical mechanisms underlying the enhanced performance, and highlight emerging opportunities and challenges for future research in complex metasurface architectures.