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17 pages, 5894 KiB

Open AccessArticle

Wave Propagation in Periodic Metallic Structures with Equilateral Triangular Holes

by Antonio Alex-Amor, Guido Valerio, Fatemeh Ghasemifard, Francisco Mesa, Pablo Padilla, José M. Fernández-González and Oscar Quevedo-Teruel

Appl. Sci. 2020, 10(5), 1600; https://doi.org/10.3390/app10051600 - 28 Feb 2020

Cited by 13 | Viewed by 2771

Abstract

This paper studies wave propagation in a periodic parallel-plate waveguide with equilateral triangular holes. A mode-matching method is implemented to analyze the dispersion diagram of the structure possessing glide and mirror symmetries. Both structures present an unexpected high degree of isotropy, despite the [...] Read more.

This paper studies wave propagation in a periodic parallel-plate waveguide with equilateral triangular holes. A mode-matching method is implemented to analyze the dispersion diagram of the structure possessing glide and mirror symmetries. Both structures present an unexpected high degree of isotropy, despite the triangle not being symmetric with respect to rotations of 90°. We give some physical insight on the matter by carrying out a modal decomposition of the total field on the hole and identifying the most significant modes. Additionally, we demonstrate that the electrical size of the triangular hole plays a fundamental role in the physical mechanism that causes that isotropic behavior. Finally, we characterize the influence of the different geometrical parameters that conform the unit cell (period, triangle size, hole depth, separation between metallic plates). The glide-symmetric configuration offers higher equivalent refractive indexes and widens the stopband compared to the mirror-symmetric configuration. We show that the stopband is wider as the triangle size is bigger, unlike holey structures composed of circular and elliptical holes where an optimal hole size exists. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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10 pages, 2882 KiB

Open AccessArticle

A Dual-Beam Leaky-Wave Antenna Based on Squarely Modulated Reactance Surface

by Hao Yu, Kuang Zhang, Xumin Ding and Qun Wu

Appl. Sci. 2020, 10(3), 962; https://doi.org/10.3390/app10030962 - 02 Feb 2020

Cited by 11 | Viewed by 3312

Abstract

In this paper, a novel dual-beam leaky-wave antenna (LWA) based on squarely modulated reactance surface (SquMRS) is proposed. The equivalent transmission lines model is utilized to characterize the field distributions of surface wave guided by the SquMRS. The calculated dispersion characteristics of SquMRS [...] Read more.

In this paper, a novel dual-beam leaky-wave antenna (LWA) based on squarely modulated reactance surface (SquMRS) is proposed. The equivalent transmission lines model is utilized to characterize the field distributions of surface wave guided by the SquMRS. The calculated dispersion characteristics of SquMRS are verified by the simulated results, and it is demonstrated that SquMRS exhibits a more flexible control of phase constant and attenuation constant compared with traditional sinusoidally modulated reactance surface (SinMRS), which means SquMRS has a great potential for near-field focusing and far-field beam shaping. On this basis, a versatile method, based on a superposition of individual modulation patterns, was used to generated two beams with almost identical gain at 8.5 GHz. The measured results show that the gains are 10 dBi and 8.2 dBi at θ₁ = −30° and θ₂ = 18°, respectively, and the radiation efficiency is 83%, which shows good agreement with the simulated results. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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10 pages, 5191 KiB

Open AccessArticle

Ultrathin Acoustic Metasurface Holograms with Arbitrary Phase Control

by Huaping Wang, Weijie Gao, Rongrong Zhu, Zehao Wang, Zhiwei Xu and Bin Zheng

Appl. Sci. 2019, 9(17), 3585; https://doi.org/10.3390/app9173585 - 02 Sep 2019

Cited by 8 | Viewed by 6179

Abstract

Holograms show great potential in optical or acoustical waves applications due to their capability to reconstruct images. In this paper, we propose a novel scheme to realize acoustic holograms based on an ultrathin metasurface with arbitrary phase control ability. Compared with the conventional [...] Read more.

Holograms show great potential in optical or acoustical waves applications due to their capability to reconstruct images. In this paper, we propose a novel scheme to realize acoustic holograms based on an ultrathin metasurface with arbitrary phase control ability. Compared with the conventional imaging method, e.g., concave mirror, which has a bulky size and limited imaging effects, the acoustic metasurface comprises a single layer of Helmholtz-like elements that can largely reduce the complexity of production. With this ultrathin reflective metasurface, acoustic holograms are constructed through a subtle structure design for single and multiple focal imaging, while the potential thermoviscous effects are minimized. We further demonstrate that the metasurface has the capability of arbitrary phase control in a certain frequency range, where the reflected phase dispersion is linear. Our proposed ultrathin metasurface holograms would be very useful in numerous applications, such as acoustic sensing, medical imaging, and so on. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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13 pages, 7554 KiB

Open AccessFeature PaperArticle

Oblique Wide-Angle Multi-Sector Metamaterial Absorber for Space Applications

by Olivier Rance, Anne Claire Lepage, Xavier Begaud, Kevin Elis and Nicolas Capet

Appl. Sci. 2019, 9(16), 3425; https://doi.org/10.3390/app9163425 - 20 Aug 2019

Cited by 5 | Viewed by 3363

Abstract

This article presents the design, realization and measurement of lightweight absorbing material for space applications. The electromagnetic absorber, operating on the [2 GHz, 2.3 GHz] frequency band, is designed for oblique incidence ranging from 35° to 65°. Wide-angle designs are demonstrated to be [...] Read more.

This article presents the design, realization and measurement of lightweight absorbing material for space applications. The electromagnetic absorber, operating on the [2 GHz, 2.3 GHz] frequency band, is designed for oblique incidence ranging from 35° to 65°. Wide-angle designs are demonstrated to be particularly challenging at oblique incidence and an approach consisting in dividing the surface in two different sectors with respect to the incoming angle is proposed. A specific measurement setup is presented in order to characterize this new kind of evolutive absorber. The measurement results show that the sectorial absorber achieves a reflection coefficient inferior to −11.5 dB, corresponding to an absorptivity above 0.965 on the frequency band [2 GHz, 2.3 GHz] for both TE and TM polarizations for angles of incidence varying from 35° to 65°. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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10 pages, 3782 KiB

Open AccessArticle

Tunable Beam Steering, Focusing and Generating of Orbital Angular Momentum Vortex Beams Using High-Order Patch Array

by Zhiping Yin, Qun Zheng, Kai Guo and Zhongyi Guo

Appl. Sci. 2019, 9(15), 2949; https://doi.org/10.3390/app9152949 - 24 Jul 2019

Cited by 20 | Viewed by 4334

Abstract

In this paper, a tunable patch array based on high-order is proposed at the frequency of 300 GHz, achieving active controllable beam steering, focusing and generation of orbital angular momentum vortex beams. It has been demonstrated that the patch array can achieve wide [...] Read more.

In this paper, a tunable patch array based on high-order is proposed at the frequency of 300 GHz, achieving active controllable beam steering, focusing and generation of orbital angular momentum vortex beams. It has been demonstrated that the patch array can achieve wide beam scanning angle by controlling the phase of array elements with tunable phase shifters. Meanwhile, beam focusing on the specified position can also be realized by phase modulation of array elements based on the focusing theory. In addition, we also designed a patch array to generate vortex beams with multiple topological charges by high-order modes. The performances show that the patch antenna array we designed has a good application prospect. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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13 pages, 9251 KiB

Open AccessArticle

Design and Application Research of All-Dielectric Nanostructure Colorful Display

by Shishang Luo, Junbo Yang, Xin He, Sen Zhang and Ying Chen

Appl. Sci. 2019, 9(14), 2937; https://doi.org/10.3390/app9142937 - 23 Jul 2019

Cited by 3 | Viewed by 2657

Abstract

Structural colors generated by plasmonic resonances in metallic nanostructures have been intensively studied and exciting progress has been made. However, because of the inherent plasmon damping, the saturation of these colors generated by metallic nanostructures could not meet the needs of industrial applications. [...] Read more.

Structural colors generated by plasmonic resonances in metallic nanostructures have been intensively studied and exciting progress has been made. However, because of the inherent plasmon damping, the saturation of these colors generated by metallic nanostructures could not meet the needs of industrial applications. As a result, researchers increasingly focus on structural colors generated by all-dielectric nanostructures. In this paper, we discuss a type of all-dielectric nanostructure based on a previous design and analyze its optical properties extensively. The display of character T with different color is realized by using this nanostructure. The study helps the understanding of the influence of structural parameters on structural color and provides some guidance for future experiments. This work can impact the development of the structural color devices which can be applied in color printing, color displays, color filters, imaging, and energy harvesting, etc. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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14 pages, 6665 KiB

Open AccessArticle

Metasurface Antennas Embedded in Small Circular Cavities for Telemetry Applications

by Loïc Bernard, Mario Martinis, Sylvain Collardey, Kouroch Mahdjoubi and Ronan Sauleau

Appl. Sci. 2019, 9(12), 2496; https://doi.org/10.3390/app9122496 - 19 Jun 2019

Cited by 3 | Viewed by 3507

Abstract

This paper introduces a metasurface-inspired antenna embedded in a circular metallic cavity with a very small diameter (from 0.25 λ₀ down to 0.12 λ₀, where λ₀ is the wavelength in vacuum at the operating frequency). The proposed concept is [...] Read more.

This paper introduces a metasurface-inspired antenna embedded in a circular metallic cavity with a very small diameter (from 0.25 λ₀ down to 0.12 λ₀, where λ₀ is the wavelength in vacuum at the operating frequency). The proposed concept is introduced and explained: It consists of placing a capacitive surface at the cavity aperture. This capacitive effect is obtained using multi-layer capacitively coupled strips. Our numerical results demonstrate that the impedance bandwidth is larger than that of standard patch antennas embedded in the same cavity size. Various prototypes have been manufactured, and measurements are found to be in good agreement with numerical results in all cases. The practical applications of these small metasurface antennas are demonstrated with telemetry applications for flying vehicles. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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12 pages, 4087 KiB

Open AccessArticle

Perforated Medium Applied in Frequency Selective Surfaces and Curved Antenna Radome

by Zhonghang Duan, Gheit Abomakhleb and Guizhen Lu

Appl. Sci. 2019, 9(6), 1081; https://doi.org/10.3390/app9061081 - 14 Mar 2019

Cited by 5 | Viewed by 3703

Abstract

A perforated medium (PM) combined with an ultra-wideband frequency selective surface (FSS) is proposed for the antenna radome design, which provides more flexibility in the radome materials selection and processing. The dielectric constant performance of the PM can be improved by perforating air [...] Read more.

A perforated medium (PM) combined with an ultra-wideband frequency selective surface (FSS) is proposed for the antenna radome design, which provides more flexibility in the radome materials selection and processing. The dielectric constant performance of the PM can be improved by perforating air holes through the medium, thus the restrictions of the FSS medium material parameters can be released. A multiscale homogenization method is utilized to calculate the dielectric constant of this PM, and the transmission coefficients of the planar FSS structure at different incidence angles are computed. The PM FSS is then applied in the curved antenna radome. The physical optic method serves to analyze the transmission performance of the curved antenna radome. In order to reduce the computational difficulties and meet the requirements of physical optic computing, the transmission coefficients are obtained as a function of the frequency by the vector fitting method, and the incidence angle dependence is deduced by B spline interpolation. The simulated and experimental radiation patterns with and without the radome are compared and the results show good agreement. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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11 pages, 3774 KiB

Open AccessArticle

AdjusTable 3D Plasmonic Archimedes Spiral Lens for Optical Manipulation

by Lin Cheng, Xiaomingliang Li, Zelong Wang, Pengfei Cao, Xiaodong He and Tiaoming Niu

Appl. Sci. 2019, 9(4), 674; https://doi.org/10.3390/app9040674 - 16 Feb 2019

Cited by 5 | Viewed by 3156

Abstract

A novel adjustable three-dimensional plasmonic Archimedes spiral lens (3D PASL) has been investigated and analyzed in detail by numerical simulations. The 3D PASL consists of a spiraling Archimedes helix slot that is engraved on the inner wall of a funnel-shaped gold film on [...] Read more.

A novel adjustable three-dimensional plasmonic Archimedes spiral lens (3D PASL) has been investigated and analyzed in detail by numerical simulations. The 3D PASL consists of a spiraling Archimedes helix slot that is engraved on the inner wall of a funnel-shaped gold film on a silicon dioxide substrate. When the incident light from the bottom of substrate is composed of left-hand circularly polarized (LCP) waves, the transmitted light field will converge completely to a focused point that floats in the hollow funnel. This light field will change into an optical vortex when the incident light is changed to right-hand circularly polarized (RCP) waves. The performance of our 3D PASL is discussed for particle trapping or rotation applications. In addition, the position of the optical focus or vortex can be adjusted by varying the height of the structure. Our 3D PASL is highly flexible for practical optical manipulation applications and overcomes the problem where the previous two-dimensional PASL could only manipulate particles on the surface. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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Review

Jump to: Research

22 pages, 12320 KiB

Open AccessReview

A Review of Orbital Angular Momentum Vortex Beams Generation: From Traditional Methods to Metasurfaces

by Kuang Zhang, Yuxiang Wang, Yueyi Yuan and Shah Nawaz Burokur

Appl. Sci. 2020, 10(3), 1015; https://doi.org/10.3390/app10031015 - 04 Feb 2020

Cited by 74 | Viewed by 10481

Abstract

In this paper, we review the generation of vortex beams carrying orbital angular momentum in the microwave domain. We firstly present the theory of Laguerre–Gaussian beams where it is demonstrated that they carry such type of momentum. We further provide an overview of [...] Read more.

In this paper, we review the generation of vortex beams carrying orbital angular momentum in the microwave domain. We firstly present the theory of Laguerre–Gaussian beams where it is demonstrated that they carry such type of momentum. We further provide an overview of the classical methods used to generate orbital angular momentum vortex beams, which rely on two main methods; plane wave to vortex wave conversion and direct generation using radiating antennas. Then, we present recent progress in the physics of metasurfaces devoted to the generation of vortex beams with a discussion about reflective and transmissive metasurfaces for plane wave to vortex wave conversion as well as methods to reduce the intrinsic divergence characteristics of vortex beams. Finally, we conclude on this rapidly developing research field. Full article

(This article belongs to the Special Issue Advanced Active and Passive Metasurfaces)

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