Ultrathin Metamaterial Absorber Research Articles

Design of an ultra-thin quad-band metamaterial absorber for sensing and antenna performance enhancement

Design of an ultra-thin quad-band metamaterial absorber for sensing and antenna performance enhancement

A novel, mutual coupling independent, ultra-thin, and polarization-insensitive tetra band metamaterial absorber for microwave applications

This manuscript presents a novel, highly efficient, wide-angle, and polarization-stable symmetrical single-layered metamaterial absorber (MA) on a 0.8 mm thin dielectric layer that exhibits four distinct absorption peaks having 0.019 λ ∘ , 0.027 λ ∘ , 0.038 λ ∘ , and 0.044 λ ∘ , respectively. The amalgamation of two circular rings surrounded by a square-shaped four split ring resonators (RR) including a combined group of a circular patch and a square ring in a unit cell enabled mutually coupling independent environment amongst the inter-elements and resulted in a compact geometry. The inclusion of the relevant sub-elements in the proposed MA demonstrated polarization-insensitive characteristics over wide angles of incident waves for both transverse electric (TE) and transverse magnetic (TM) at four frequency bands, i.e. 7.16 GHz, 10.175 GHz, 12.92 GHz, and 16.82 GHz having 99.6%, 97.2%, 98.3%, and 94.8% absorptivity, respectively. The experimental validation of the prototype to validate the simulated results is performed in an anechoic chamber.

Compact polarization-insensitive microwave metamaterial absorber with hepta-band characteristics

This paper presents an ultra-thin and compact metamaterial absorber (MMA) capable of achieving near-perfect absorption peaks across the C, X, Ku, and K frequency bands. The MMA structure features a modified metallic plus-shaped resonator surrounded by symmetric L-shaped resonators within a compact size of 13 × 13 mm2. The absorber exhibits seven absorption peaks at different resonant frequencies including 4.23, 6.48, 10.62, 12.92, 14.03, 17.39, and 18.11 GHz. With a thickness of 0.0225λ and a compact size of 0.1833λ at the lowest frequency, the absorber offers remarkable thinness and compactness. Different characteristics of the absorber, such as normalized impedance, surface current distribution, and electric field distribution, are also examined. The polarization-insensitive behavior of the MMA is assessed through absorption and reflection responses under different polarization and incident angles. The Equivalent Circuit Model (ECM) of the metamaterial absorber is also designed to accurately represent the MMA unit cell across all resonant frequencies. Experimental validation of the proposed MMA confirms its performance consistency with simulation results. The proposed MMA design holds potential for applications in defense, detection, and sensing. The sensing ability of the MMA is analyzed using simulations at different refractive index values.

Design of ultra-thin multi-band sub-terahertz metamaterial absorber using three concentric ring resonators with same opening direction

In this paper, an ultra-thin sub-terahertz multi-band terahertz metamaterial absorber is proposed, its cell consists of three concentric ring resonators with the same opening direction, which can realize three discrete absorption peaks in the sub-terahertz frequency domain. The absorption peaks are mainly formed when the three open circular resonators interact with each other, and the superposition of the three discrete peaks creates a three-band absorption. The physical mechanisms of three-band absorption are illustrated by the electric fields and surface current distributions of three absorption peaks. Adjustment of the absorption effect could be obtained by altering the dimensions of the cleft circular resonator. By fixing the dimensions and changing the opening direction, these resonators will couple to each other and play an important role in regulating the frequency, intensity, and number of absorption peaks. Moreover, the multi-band metamaterial structure could be combined with vanadium dioxide, a phase change material, to actively modulate the absorption. In addition, the three-band metamaterial absorber has the characteristics of polarization-sensitive and wide-angle, which has extensive applications in the domains of security detection, biomedicine and communication.

Ultra-thin wideband frequency tunable metamaterial absorber and its application for antenna radar cross section reduction

A metamaterial absorber (MMA) with broadband and efficient absorption performance based on ultra-thin dielectric layer is proposed. In this unique configuration, the absorption frequency of the MMA can be continuously and dynamically tuned across a wide frequency range by manipulating the reverse voltage of the central varactor diode. From both the equivalent circuit and field distribution perspectives, we analyze the mechanisms behind broadband tuning and superior absorption. Simulation and experimental results demonstrate that the absorption peak of MMA can be continuously tuned over a range of 5.16–8.16 GHz, with the absorption rate consistently exceeding 90%, and the thickness is only 0.5 mm. Integrating MMA array with a microstrip patch antenna in a suitable manner can dynamically mitigates the radar cross section (RCS) within the associated frequency range, with virtually negligible impact on the antenna’s radiation performance.

Penta-band polarization insensitive ultra-thin metamaterial absorber suitable for flux shielding in WPT

This study introduces a novel multi-band, polarization-insensitive metamaterial absorber, designed by combining a dual-band and a triple-band resonator structures. Through the amalgamation of discrete absorption responses from these structures, the resulting design exhibits five absorption peaks at frequencies: 1.5 GHz (80%), 3.6 GHz (88%), 5.46 GHz (95%), 7.17 GHz (95%), and 9.17 GHz (95%). One of the standout features of the proposed design lies in its four-fold symmetry, endowing it with polarization insensitivity. This ensures robust performance regardless of the incident polarization, enhancing the versatility and applicability of the absorber in various scenarios. The design’s compact nature is noteworthy, with a unit cell dimension of only 0.125λ. This compactness not only contributes to space-efficient deployment but also underscores the efficiency of the metamaterial in achieving multiple absorption peaks within a limited spatial footprint. In addition to its compactness, the absorber is ultra-thin, with a dielectric thickness of merely 0.008λ. This characteristic is particularly advantageous for applications where a low-profile and lightweight solution is essential, such as in the development of inconspicuous communication devices or electromagnetic shielding.

Large-Scale Fabrication of Customized, Tunable, Ultrathin, and Flexible Metamaterial Absorbers Based on Laser-induced Graphene

Developing various 3D graphene microwave absorbers is a hotspot strategy to address the issue of continuous electromagnetic pollution, but remains great challenges in realizing high-performance microwave absorption capability at thin thickness. Herein, a series of flexible metamaterial absorbers (MAs) composed of periodical laser-induced graphene (LIG) surface, dielectric substrate and metallic ground fabric from top to bottom are fabricated. The LIG meta-surface is customized by means of regulating parameters including laser power density (LPD), laser engraving rate (LER) and input patterns to well balance impedance matching and electromagnetic loss. LIG MAs exhibit minimum reflection loss (RL) of −39.7 dB (with effective absorption bandwidth (EAB) of 5.5 GHz) and maximum EBA of 12.1 GHz (with RL of −18.9 dB) at thickness less than 1.1 mm, and the simulated and experimental results are highly consistent. In addition, radar cross section (RCS) simulation of LIG MA with multi-angles endows its potential for prospective applications in in-orbit satellites electromagnetic protection.

Ultra-Thin and Broadband P-Band Metamaterial Absorber Based on Carbonyl Iron Powder Composites.

The field of P-band (0.3-1 GHz) absorption has witnessed rapid development in metamaterial absorbers due to their exceptional designability and the absence of restrictions imposed by the one-fourth wavelength rule. In this study, we combined carbonyl iron powder (CIP) composites with a periodic structure composed of metal capacitive patterns and employed a genetic algorithm (GA) to optimize the electromagnetic parameters of the CIP substrate. By selecting the appropriate shape and material for the units of pattern based on transmission line theory, as well as regulating relevant structural parameters, we successfully designed an ultra-thin broadband metamaterial absorber for the P-band. Experimental results demonstrate that within the range of 0.3-0.85 GHz, the reflection loss of our absorber remains below -5 dB, with a maximum value of -9.54 dB occurring at 0.45 GHz. Remarkably, this absorber possesses a thickness equivalent to only 1/293 of its working wavelength. Then, we conducted analyses on electric field distribution, magnetic field distribution, and energy loss density. Our findings suggest that high-performance absorption in metamaterials can be attributed to λ/4 resonant or coupling effects between structural units or diffraction phenomena. This absorber offers several advantages, including broad low-frequency absorption capability, ultra-thin profile, and convenient fabrication process, thus providing valuable theoretical insights for designing metamaterial structures.

A low-frequency ultrathin metamaterial absorber using magnetic material

In this paper, an ultra-thin metamaterial absorber (UMA) in the S-band is designed. The overall structure adopts a three-layer design. The top layer is a magnetic material, and the middle layer of the UMA is composed of a centrally symmetrical open square ring (four edges are opened) and a circular pattern placed at the center, which is etched on the FR4 dielectric substrate by printed circuit board technology. The absorptivity of the absorber is more than 90% in 1.73–4.04 GHz under normal incidence, and the fractional bandwidth is 80.1%. The total thickness of the absorber is about 3.4 mm, corresponding to 0.02 λL at the lowest operating frequency. Moreover, it also has good polarization insensitivity and wide-angle incident characteristics. The absorption mechanism of the UMA is analyzed from the aspects of power loss density and surface current. Finally, a sample was fabricated and measured. The measured results are in good agreement with the simulation results, which verifies the effectiveness of the design method.

Design and equivalent circuit modelling of super compact ultrathin metamaterial absorber for microwave frequency Regime

Abstract This article is an attempt to design and develop a metamaterial-based microwave absorber with a low profile, broad incidence angle and compactness in the microwave frequency range. Further, equivalent circuit model of the proposed structure is discussed based on circuit theory. The unit cell focuses on achieving maximum absorption at C-, X-, and K-band. The dimensions of the proposed design are ultrathin and compact, having an overall size of 8 mm × 8 mm × 0.8 mm. The dimensions are optimized in such a fashion to achieve three different peaks at three various bands (C, X and K), thereby making the triple-band behaviour of the metamaterial absorber possible. The structure provides absorption of 98.26 % absorption at 7.76 GHz (C-band) while absorption of 96.74 % is achieved at 10.26 GHz (X-band) and 99.92 % absorption at 19.32 GHz (K-band) of microwave regime. The experimental verification of design conform that the measured results are found to be in close agreement to simulated ones.

Optimization of ultrathin polarization insensitive metamaterial absorbers using trust region algorithm based on Co-kriging model

In this paper, a trust region optimization algorithm integrated with a co-kriging surrogate-model is newly formulated to optimize compact ultrathin wideband metamaterial absorbers with high absorption. The reported algorithm is linked with the full vectorial finite element method to simulate and optimize the studied absorbers. In order to show the power of the suggested algorithm, the geometrical parameters of a previous metamaterial absorber (MA) with L-shaped resonators are optimized to achieve high absorption (over 90 %) over a frequency band from 13.8 GHz to 24.5 GHz covering most of KU and K bands. Then, a novel design of L-shaped MA with triangular resonators is optimized, analyzed and fabricated with high absorption (above 90 %) through a large frequency band from 11.9 GHz to 22 GHz covering the entire KU-band and most of the K-band. The reported design is also robust against the variations of the incident angle (above 80 % up to 50°) for both transverse electric (TE) and transverse magnetic (TM) polarized modes. Therefore, the proposed algorithm could be used efficiently for the design and optimization of metamaterial absorbers.

Ultrathin Flexible Terahertz Metamaterial Absorber with High Sensitivity for Bending Strain Sensing

Ultrathin Flexible Terahertz Metamaterial Absorber with High Sensitivity for Bending Strain Sensing

Design and analysis of a compact ultrathin penta-band metamaterial absorber

Design and analysis of a compact ultrathin penta-band metamaterial absorber

Polarization-insensitive Archimedes’-spiral-shaped ultrathin metamaterial absorbers for microwave sensing application

This work has developed and simulated a planar complementary Archimedes-based metamaterial absorber with the goal of its application in refractive index sensing. Unlike designs that employ multiple layers or numerous resonators within a single unit cell, our proposed absorber adopts a more streamlined approach. It consists of three layers, with an FR4 dielectric substrate sandwiched between two copper layers. It's important to note that the absorption characteristics of this design are polarization-dependent. This polarization dependence arises from the asymmetrical resonance behavior observed in both the x and y directions. The absorber exhibits impressive absorption rates at various resonance frequencies, namely 98.5% at f1 = 8.49 GHz, 77.1% at f2 = 8.88 GHz, 88.7% at f3 = 9.3 GHz, 98.2% at f4 = 9.87 GHz, 99.7% at f5 = 10.65 GHz, 83.4% at f6 = 11.58 GHz, and 99.9% at f7 = 12.24 GHz. Furthermore, the article explored the refractive index sensing capabilities of this structure by introducing a 1 mm analyte layer on top of the patch structure. Through refractive index sensing analysis, we've determined that this absorber-based sensor yields an impressive high-quality factor value of 84.5, highlighting its remarkable sensitivity and precision. A more profound comprehension of the physical mechanisms in action has been attained by examining the distribution of surface currents. Furthermore, the behavior of the absorber has been investigated under varying polarization and incident angle conditions, ranging from zero degrees to sixty degrees. The thorough characterization establishes this absorber as a promising choice for microwave sensing applications.

An ultra-thin, polarization free wide-angle stable quad-band metamaterial absorber for applications in C, X, and Ku bands

This study proposes and examines an ultrathin, wide-angle stable and polarization-insensitive metamaterial absorber (MMA) with quad-band functionalities. The proposed MMA exhibits four absorption peaks of 95.67%, 99.16%, 95.97%, and 97.02% at 5.026 GHz, 8.582 GHz, 11.73 GHz, and 15.036 GHz, respectively. The corresponding full width at half maximum (FWHM) bandwidth observed from simulations of the proposed MMA is found to be 180 MHz, 360 MHz, 420 MHz, and 580 MHz. It has a thickness of 0.0134 λ0 and the dimension of the unit cell is 0.167 λ0 × 0.167 λ0 at 5.026 GHz. Moreover, it does not display any variations in absorption performance when polarization angle (ϕ) is changed, justifying its polarization insensitive behavior. When changing the incident angle (θ) in case of oblique incidence, the proposed MMA is able to maintain the absorptivity above 90% for transverse electric (TE) mode up to 30° and for transverse magnetic (TM) mode up to 60° at all four frequency, which demonstrates its angular stable characteristics. Analyses of the variation in structural parameter, complex permittivity, complex permeability, surface current density, absolute electric field, and normalized input impedance have also been carried out to authenticate the proposed MMA unit cell structure.

Wideband ultrathin and polarization insensitive metamaterial absorber for Ku-band applications

In this paper, wideband, and ultrathin metamaterial absorber is proposed, analyzed and fabricated for Ku-band applications. The reported absorber has a nearly perfect absorptivity above 90% covering the entire Ku band (12–20 GHz) at normal incidence for both transverse electric and transverse magnetic polarization. This is due to the supported electric and magnetic resonances simultaneously. Consequently, the effective permittivity and permeability can be designed to obtain impedance matching with free space. This leads to the absorption of the entire incident energy in the metamaterial absorber. The suggested structure also shows a good absorption response (above 80%) under oblique incidence (from 0 to 50°). Therefore, the proposed absorber represents a good potential for Ku-band applications.

Polarization insensitive oblique incident angle stable ultra-thin nano ring resonator-based metamaterial absorber for visible and near-infrared region applications

Polarization insensitive oblique incident angle stable ultra-thin nano ring resonator-based metamaterial absorber for visible and near-infrared region applications

Quantum Inspired Broadband Photonic Absorber: Potential Application as Solar Sail along with Mobility Analysis

Electromagnetic wideband absorption is still perceived as a critical and formidable challenge to address with an unambiguous photonic absorber. Subwavelength metamaterial (MM) unit cells with unique and controlled features have recently gained considerable interest. However, meta‐atoms, generated using a quantum‐inspired pattern distribution, are underwhelming in existing literature to design photonic absorbers and their potential application to manufacture solar sails is still quite uncommon. In this article, to create a flexible, polarization‐insensitive, ultrathin, and broadband MM absorber, quantum interference pattern‐inspired design is utilized. Herein, a novel approach to fabricating solar sails for the space exploration incorporates the proposed broadband photonic absorber rather than conventional reflectors. The quantum‐inspired meta‐absorber (QIMA) exhibits an absorption of over 91% for the visible domain, i.e., 380–800 nm under a conventional plane‐polarized source. It is shown in the study that broadband absorbers are almost equivalent to excellent reflectors to design the solar sails in terms of the time‐averaged force calculated by utilizing the Maxwell stress tensor method. Thus, the QIMA has the potential to be a viable alternative to reflectors in the design of futuristic solar sails for space exploration. The interference theory model is also utilized to assure the dependability of calculated data, and additionally, the standard AM1.5 solar spectrum is utilized to demonstrate the QIMA's solar‐harvesting potentiality.

Highly effective gallium arsenide split-disk resonator-based ultrathin metamaterial absorber

Highly effective gallium arsenide split-disk resonator-based ultrathin metamaterial absorber

Broadband polarization insensitive metamaterial absorber

Ultrathin and broadband metamaterial absorber with loaded four lumped resistors is proposed and analyzed. The reported design is based on increasing the absorptivity by reducing the reflection and transmission coefficients simultaneously. Therefore, continuous metallic ground is used to achieve zero transmission while the reflection is reduced by matching the impedance of the proposed metamaterial absorber with the impedance of free space (Z = Z0 or μr = εr). Additionally, electric and magnetic resonances are achieved simultaneously with perfect absorptivity. The finite element method is used to simulate and analyze the reported absorber. The suggested absorber shows higher absorption than 90% over large frequency range (14.35–29.18 GHz) for both transverse electric and transverse magnetic polarizations. Further, the proposed design has high absorption through incident angle variation from 0° to 50°. Therefore, the reported perfect metamaterial absorber has good potential applications in communications, stealth and imaging fields.