Cascade-To-Single Layer Transformation of Multifunctional Multispectral Metasurfaces.

Multifunctional metasurfaces are commonly realized using cascaded or few-layer architectures, in which each layer performs a dedicated electromagnetic function. Although such designs offer increased degrees of freedom and high efficiency, they inevitably increase overall thickness and fabrication complexity. Achieving comparable multifunctional performance within a single-layer metasurface therefore constitutes a more compact and practically attractive solution. Here, we show that a five-function cascaded metasurface can be systematically collapsed into a single-layer metasurface while preserving electromagnetic functionality and efficiency. The proposed design employs a helix-inspired supercell architecture that integrates multiple frequency-selective meta-atoms within a single planar layer. Each meta-atom operates independently at a designated frequency, enabling polarization-selective reflection and transmission, circular-polarization conversion, and absorption in an ultrathin layer. Full-wave simulations confirm that the single-layer metasurface reproduces the performance of its cascaded counterpart with high efficiency, polarization robustness, and angular stability across all operating bands. These results establish an approach for translating cascaded metasurface architectures into single-layer implementations, providing a scalable pathway toward ultracompact multifunctional electromagnetic devices.