Efficient anomalous reflection through near-field interactions in metasurfaces

Chalabi, Hamidreza; Ra’di, Younes; Sounas, Dimitrios L.; Alù, Andrea

doi:10.1103/physrevb.96.075432

Cited by 79 publications

(60 citation statements)

References 34 publications

(21 reference statements)

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“…Lately, analytical models for electrically-polarizable MGs were developed, relying on arrays of dielectric rods [20] or capacitively-loaded wires [21] for achieving wideangle anomalous reflection and beam splitting. In fact, the theoretical framework was augmented in [21] to allow complete semianalytical design of the MG, up to the conductor geometry of the printed capacitors.…”

Section: Introductionmentioning

confidence: 99%

Experimental demonstration and in-depth investigation of analytically designed anomalous reflection metagratings

et al. 2019

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We present the design, fabrication and experimental investigation of a printed circuit board (PCB) metagrating (MG) for perfect anomalous reflection. The design follows our previously developed analytical formalism, resulting in a single-element MG capable of unitary coupling of the incident wave to the specified (first order) Floquet-Bloch (FB) mode while suppressing the specular reflection. We characterize the MG performance experimentally using a bistatic scattering pattern measurement, relying on an original beam-power integration approach for accurate evaluation of the coupling to the various modes across a wide frequency range. The results show that highly-efficient wide-angle anomalous reflection is achieved, as predicted by the theory, with a relatively broadband response. In addition, the MG is found to perform well when illuminated from different angles, acting as a multichannel reflector, and to scatter efficiently also to higher-order FB modes at other frequencies, exhibiting multifunctional capabilities. Importantly, the merits of the introduced beam-integration approach, namely, its improved resilience to measurement inaccuracies or noise effects, and the implicit accommodation of different effective aperture sizes, are emphasized, highly relevant in view of the numerous recent experimental reports on anomalous reflection metasurfaces. Finally, we discuss the source for losses associated with the MG; interestingly, we show that these correlate well with edge diffraction effects, rather than (commonly assumed) power dissipation. These experimental results verify our theoretical synthesis scheme, showing that highly-efficient anomalous reflection is achievable with a realistic fabricated MG, demonstrating the practical applicability and potential mutifunctionality of analytically designed MGs for future wavefront manipulating devices.

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Section: Introductionmentioning

confidence: 99%

Experimental demonstration and in-depth investigation of analytically designed anomalous reflection metagratings

et al. 2019

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“…In this paper, we mitigate these issues by introducing a systematic rigorous methodology to design fabrication-ready multilayered multielement metagratings (MGs) for arbitrary diffraction engineering, without as much as a single simulation in a full-wave solver. Based on the recently proposed idea of single-or dual-element MGs for perfect anomalous reflection, systematically put forward in [42], [43], we show that the (forward and backward) scattering to multiple FB modes can be simultaneously controlled, in both amplitude and phase, by a properly engineered distribution of multiple metaatoms across multiple dielectric layers ( Fig. 1).…”

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confidence: 87%

Arbitrary Diffraction Engineering With Multilayered Multielement Metagratings

Rabinovich

Epstein

2020

IEEE Trans. Antennas Propagat.

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We theoretically formulate and experimentally demonstrate an analytical formalism for the design of printed circuit board (PCB) metagratings (MGs) exercising individual control over the amplitude and phase of numerous diffracted modes, in both reflection and transmission. Lately, these periodic arrangements of subwavelength polarizable particles (metaatoms) were shown to deflect an incoming plane wave to prescribed angles with very high efficiencies, despite their sparsity with respect to conventional metasurfaces. Nonetheless, most reported MGs were designed based on full-wave optimization of the meta-atoms, with the scarce analytical schemes leading directly to realizable devices were restricted to single-layer reflecting structures, controlling only the partition of power. In this paper, we present an analytical model for plane-wave interaction with a general multilayered multielement MG, composed of an arbitrary number of meta-atoms distributed across an arbitrary number of layers in a given stratified media configuration. For a desired (forward and backward) diffraction pattern, we formulate suitable constraints, identify the required number of degrees of freedom, and correspondingly set them to yield a detailed MG configuration implementing the prescribed functionality; no full-wave optimization is involved. To verify and demonstrate the versatility of this systematic approach, fabrication-ready multilayer PCB MGs for perfect anomalous refraction and non-local focusing are synthesized, fabricated, and experimentally characterized, for the first time to the best of our knowledge, indicating very good correspondence with theoretical predictions. Importantly, the formalism also accounts for realistic conduction losses, critical to obtain reliable efficient designs. This appealing semianalytical methodology is expected to accelerate the development of MGs and extend the relevant range of applications, yielding practical MG designs on demand for arbitrary beam manipulation.

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“…Early works on near-field interaction in metamaterials aimed to model the propagation of magneto-inductive waves in arrays of split ring resonators [23], to analyze tunability through modifying lattice parameters [24] and to analyze optical activity of twisted dimers [25,26]. Furthermore, several recent works propose analytical de-sign approaches for metagratings based on rigorous descriptions of the mutual interaction of individual particles [15,[27][28][29][30]. While these works on near-field coupling in metagratings provide full insight into the interaction of individual scatterers and demonstrate highly efficient devices, they have been largely restricted to reflective operation at large angles.…”

Section: Introductionmentioning

confidence: 99%

Accurate Metasurface Synthesis Incorporating Near-Field Coupling Effects

Olk

Powell

2019

Phys. Rev. Applied

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One of the most promising metasurface architectures for the microwave and terahertz frequency ranges consists of three patterned metallic layers separated by dielectrics. Such metasurfaces are well suited to planar fabrication techniques and their synthesis is facilitated by modelling them as impedance sheets separated by transmission lines. We show that this model can be significantly inaccurate in some cases, due to near-field coupling between metallic layers. This problem is particularly severe for higher frequency designs, where fabrication tolerances prevent the patterns from being highly-subwavelength in size. Since the near-field coupling is difficult to describe analytically, correcting for it in a design typically requires numerical optimization. We propose an extension of the widely used equivalent-circuit model to incorporate near-field coupling and show that the extended model can predict the scattering parameters of a metasurface accurately. Based on our extended model, we introduce an improved metasurface synthesis algorithm that gives physical insight to the problem and efficiently compensates for the perturbations induced by near-field coupling. Using the proposed algorithm, a Huygens metasurface for beam refraction is synthesized showing a performance close to the theoretical efficiency limit despite the presence of strong near-field coupling.arXiv:1905.06475v1 [physics.optics]

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Efficient anomalous reflection through near-field interactions in metasurfaces

Abstract: Gradient metasurfaces have been extensively used in the past

Cited by 79 publications

References 34 publications

Experimental demonstration and in-depth investigation of analytically designed anomalous reflection metagratings

Experimental demonstration and in-depth investigation of analytically designed anomalous reflection metagratings

Arbitrary Diffraction Engineering With Multilayered Multielement Metagratings

Accurate Metasurface Synthesis Incorporating Near-Field Coupling Effects

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