Dual-Polarized All-Metallic Metagratings for Perfect Anomalous Reflection

TL;DR

This paper presents a theoretical and experimental approach to designing all-metallic metagratings capable of perfect anomalous reflection and dual-polarized control, using a semianalytical scheme that simplifies fabrication without full-wave optimization.

Contribution

It introduces a mode-matching formalism for designing dual-polarized all-metallic metagratings with suppressed spurious scattering, enabling efficient beam manipulation without complex optimization.

Findings

Validated designs with three prototypes demonstrating dual-polarized control.

Achieved near-perfect anomalous reflection for both TE and TM polarizations.

Provided a fabrication-ready design methodology for high-frequency applications.

Abstract

We theoretically formulate and experimentally demonstrate the design of metagratings (MGs) composed of periodic rectangular grooves in a metallic medium, intended for perfect anomalous reflection. Using mode matching, a semianalytical scheme for analysis and synthesis of such MGs, containing multiple, arbitrarily arranged, grooves per period, is derived. Following the typical MG design approach, we use this formalism to identify the relevant Floquet-Bloch (FB) modes and conveniently formulate constraints for suppression of spurious scattering, directly tying the structure's geometrical degrees of freedom (DOFs) to the desired functionality. Solving this set of constraints, in turn, yields a detailed fabrication-ready MG design, without any full-wave optimization. Besides providing means to realize highly-efficient beam deflection with all-metallic formations, we show that the rectangular (two-dimensional) groove configuration enables \emph{simultaneous} manipulation of both transverse electric (TE) and transverse magnetic (TM) polarized fields, unavailable to date with common, printed-circuit-board-based, microwave MGs. In addition, we highlight a physical limitation on the TE-polarization performance, preventing the ability to achieve perfect anomalous reflection in any desired angle. These capabilities are verified using three MG prototypes, produced with standard computer numerical control (CNC) machines, demonstrating both single- and dual-polarized control of multiple diffraction modes. These results enable the use of MGs for a broader range of applications, where dual-polarized control is required, or all-metallic devices are preferable (e.g., spaceborne systems or at high operating frequencies).