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Engineering Spatial Dispersion to Synthesize Arbitrary Spatial Filters Based on Metagratings

Jinyong Kim, Minseok Kim

TL;DR

This paper addresses the need for angularly selective spatial filters beyond fixed-incidence designs. It proposes a design framework that leverages non-uniform metagratings and engineering of the fundamental Floquet mode's spatial dispersion to synthesize prescribed angular transfer functions. The core method combines an impedance-matrix representation of mutual coupling with capacitive loading as design variables, optimized with PSO and gradient refinement to realize targeted reflection/transmission profiles across a broad incidence range. Full-wave validation at $f = 3.5\\mathrm{GHz}$ demonstrates low-pass, high-pass, and all-pass spatial filters achievable with only two sparse layers, matching analytical predictions and confirming the practical viability for compact spatial filters in communications and sensing.

Abstract

This paper presents a design framework for synthesizing angularly selective spatial filters using non-uniform metagratings. While traditional metagratings focus on channeling energy into higher-order Floquet modes for a fixed incidence angle, we leverage the fundamental mode as a versatile degree of freedom to engineer spatial dispersion over a continuous angular spectrum. By strategically distributing non-uniformly loaded metallic wires and rigorously modeling their mutual interactions through an impedance-matrix formulation, we realize prescribed angular transfer functions with high efficiency. In particular, the framework is validated at 3.5 GHz through full-wave simulations of (i) low-pass, (ii) high-pass, and (iii) all-pass spatial filters. The results demonstrate that fundamental-mode engineering in non-uniform metagratins offers a highly efficient platform for advanced spatial wave manipulation.

Engineering Spatial Dispersion to Synthesize Arbitrary Spatial Filters Based on Metagratings

TL;DR

This paper addresses the need for angularly selective spatial filters beyond fixed-incidence designs. It proposes a design framework that leverages non-uniform metagratings and engineering of the fundamental Floquet mode's spatial dispersion to synthesize prescribed angular transfer functions. The core method combines an impedance-matrix representation of mutual coupling with capacitive loading as design variables, optimized with PSO and gradient refinement to realize targeted reflection/transmission profiles across a broad incidence range. Full-wave validation at demonstrates low-pass, high-pass, and all-pass spatial filters achievable with only two sparse layers, matching analytical predictions and confirming the practical viability for compact spatial filters in communications and sensing.

Abstract

This paper presents a design framework for synthesizing angularly selective spatial filters using non-uniform metagratings. While traditional metagratings focus on channeling energy into higher-order Floquet modes for a fixed incidence angle, we leverage the fundamental mode as a versatile degree of freedom to engineer spatial dispersion over a continuous angular spectrum. By strategically distributing non-uniformly loaded metallic wires and rigorously modeling their mutual interactions through an impedance-matrix formulation, we realize prescribed angular transfer functions with high efficiency. In particular, the framework is validated at 3.5 GHz through full-wave simulations of (i) low-pass, (ii) high-pass, and (iii) all-pass spatial filters. The results demonstrate that fundamental-mode engineering in non-uniform metagratins offers a highly efficient platform for advanced spatial wave manipulation.
Paper Structure (6 sections, 7 equations, 2 figures, 1 table)

This paper contains 6 sections, 7 equations, 2 figures, 1 table.

Table of Contents

  1. Introduction
  2. CONCEPT AND DESIGN FRAMEWORK
  3. Geometry of proposed supercell
  4. Numerical Formulation of the Proposed Metagrating
  5. Optimization of Metagratings and Full-Wave Results
  6. Conclusion

Figures (2)

  • Figure 1: Front view of proposed spatial filter
  • Figure 2: (a) Schematic of simulation setup employing impedance boundaries that implement the optimized results for wires. (b)-(d) Calculated and simulated 0th-order diffraction efficiencies of the proposed metagrating-based spatial filters at 3.5 GHz: (b) Low-pass response (c) high-pass response, and (d) wide-angle transmission response with a stable efficiency profile