Wideband Metamaterial Absorber Research Articles

A wideband, thin, dual-negative, and polarization-independent square-tooth circular ring resonator-based metamaterial absorber for Ku-band applications

Abstract In the proposed paper, a novel design and realization of a wide-band, oblique angle-insensitive metamaterial absorbers are presented. The absorber is designed to work over a wide range of frequencies, making it suitable for Ku-band applications. To get wide band absorption, a novel SM-shaped design with a square-tooth circular ring resonator structure is designed efficiently. The unit cell structure is designed with a dielectric substrate (FR4) with a thickness of 3.2 mm (0.16λ0), where λ0 is the wavelength of free space. The novel design of this configuration leads to wideband absorption with respect to a conventional absorber. Several physical parameters are also investigated, such as the dielectric constant, permittivity, permeability, impedance, and negative refractive index. The simulation and experimental results show from 13.60 to 16.14 GHz with 99.1% absorption, which is excellent agreement. The analysis of the proposed design indicates that it possesses the remarkable feature of being insensitive to polarization while also exhibiting high absorption even when the angle of incidence varies. For both the simulation and experiment, results are consistent with a frequency range of 13.60–16.14 GHz for normal incidence. Almost perfect absorption works well for solar cells, EM detection, and imaging applications.

Polarization Independent Ultra-wideband Meta-material Absorber Using Conductive Ink Resonator

A wideband meta-material absorber with square and circular split rings that is based on a frequency selective surface of conductive ink is proposed. With over 90% absorptivity, the structure demonstrates broad absorption for the C, X, KU and K bands, as well as polarization independent characteristics for both TE and TM, at angles of up to 45°. Research has been performed to better understand the absorption phenomenon by looking into real and imaginary permittivity, permeability, normalized impedance, and surface current density. The meta-material absorber (MA) discussed in this study finds use in defense-related applications, such as radar surveillance, stealth technology, terrestrial and satellite communications.

Polarization insensitive passive loaded wideband metamaterial absorber

Abstract This paper proposes a lightweight frequency selective surface polarization-insensitive wideband metamaterial absorber in C band and X band that employs only a few resistive elements. The proposed absorber is embodied with four quadrature slotted inner circular patch, which is horizontally and vertically bisected, and outer concentric copper rings of 0.035 mm thickness are attached with four lumped resistors placed at 90° apart. A slotted inner circular patch provides significant inductive and capacitive loading. The absorption bandwidth of 8.02 GHz with more than 90% absorption is observed from 5.69 to 13.71 GHz under normal incidence and maintains almost same absorptivity range under oblique incidence up to 45° in both transverse electric mode and transverse magnetic mode. The designed metamaterial absorber is fabricated and measured using free space measurement technique. The actual experiments and the simulated ones are in good agreement.

Polarization-independent wideband meta-material absorber based on resistor-loaded hexagonal ring resonators

A polarization-independent meta-material-based absorber with wideband response is presented in this study. The proposed absorber’s unit cell consists of a resistance-loaded metallic hexagonal ring and four rectangular metal strips placed inside the hexagonal ring patterned on the upper surface of a dielectric substrate. The absorber exhibits wideband absorption with absorptivity more than 90% in the frequency range 7.14 to 13.68 GHz. The Full-Width Half Maxima (FWHM) of the absorber is 8.8 GHz (5.2–14 GHz). The four-fold symmetrical structure of the absorber confirms polarization-insensitive behaviour. The absorber performance is also validated with fabrication and measurement. There is a fair degree of agreement between simulated and measured results. The novelty of the proposed absorber is having wideband absorption with high packing density due to its hexagonal shape. The metamaterial absorber finds its use in defence-related applications such as radar surveillance, stealth technology, terrestrial communications, and satellite communication.

Optically transparent wideband metamaterial absorber based on equivalent aperture and characteristic mode analysis

In this work, a low-profile optical transparent wideband metamaterial absorber based on radiation–absorption reciprocal theory is proposed. The top layer and bottom layer are composed of indium tin oxide–polyethylene terephthalate films, and the middle layer is a transparent substrate polymethyl methacrylate. The method of transparent wideband absorption using reciprocal theory is proposed to guide the design. Based on characteristic mode analysis and calculated equivalent aperture efficiency, the absorber consisting of composite resonators is analyzed and designed. The equivalent circuit model and surface current distributions are studied to verify the design. The numerical results show that high absorption of greater than 90% in the frequency range of 5.7–16.4 GHz is obtained. A wideband absorption rate of greater than 80% at a 60° incident angle under TM polarization and an absorption rate of greater than 65% at a 60° incident angle under TE polarization are obtained. The proposed design has the advantages of broadband absorption, polarization insensitivity, light transmittance of more than 70%, and compact structure, which can be applied to special scenes that require optical transparency, such as anechoic chamber glass and cockpit glass.

Ni-PI-Ni based nanoarchitectonics near-perfect metamaterial absorber with incident angle stability for visible and near-infrared applications

This article presents a wideband metamaterial absorber (WMMA) for the visible and near-infrared (NIR) region application. The proposed metamaterial absorber comprises three layers of sandwiched (metal-dielectric-metal) model based on Nickel-Polyamide-Nickel. The multiple resonators on top layers achieve an average absorption of 98.16% over a range from 380 to 2300 nm with a compact unit cell size of 100 × 100 × 42 nm3. The designed WMMA shows 99% perfect absorption for a large bandwidth of 685 nm. Considering its wideband absorption, the physical absorption phenomenon was also explained in terms of the proposed WMMA's surface electric field, magnetic field, and current distribution. Also, the effects of materials and structural parameters on absorption performance with a FOM have been studied. The absorption performance is analysed with various polarization angles to demonstrate polarization insensitivity. The designed WMMA shows the absorption of >70% at large incident angles of 70°. The perceptible contribution of this WMMA is large unity absorption bandwidth at visible to NIR region with high incident angle stability, polarisation insensitivity, thermal robustness of the constituting metal and simple nanostructure geometry. Therefore, the proposed WMMA has good potential in sensors, thermal emitters, photodetectors, and absorber applications.

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.

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.

Extremely Wideband Metamaterial Absorber Using Spatial Lossy Transmission Lines and Resistively Loaded High Impedance Surface

In this article, the design, principle, and characterization of a 3-D metamaterial absorber (MA) have been presented, which consists of the spatial lossy transmission lines (SLTLs) and the resistively loaded high impedance surface (HIS). The proposed MA possesses a fractional bandwidth of 193% with absorption rate of above 90% in the frequency range from 2 to 110 GHz under TM polarization while maintaining large oblique incident angle stability of over 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\circ}$</tex-math> </inline-formula> . For demonstration, a prototype is fabricated, whose measurement results are in good agreement with the simulation results. Losses from the periodically patterned SLTLs and resistively loaded HIS are introduced by resistive graphene films using screen-printing technology, resulting in avoiding conventional soldering of numerous lumped resistors. An equivalent circuit model and a surface loss distribution are given to better illustrate the physical mechanism. Our findings establish general and systematic strategies for guiding the design of extremely wideband MA with large incident angle and pave the way for enhancing the microwave performance in applications of electromagnetic compatibility, imaging, radar detection, and stealth.

A thermocouple based on wideband hybrid metamaterial absorber for mid-infrared photo-thermoelectric detector

A mid-infrared (MIR) photo-thermoelectric (PTE) detector is proposed based on a hybrid thermocouple consisting of a wideband metamaterial absorber and Seebeck material. When a mid-infrared wave illuminates the detector, the incident energy of the MIR beam is efficiently detected in this process of converting the energy of the light wave into the absorbed heat firstly by the wideband metamaterial absorber, and then outputting a voltage change according to the variation in temperature by a semiconductor material with a high Seebeck coefficient. Because of the existence of the metamaterial absorber, the high absorptions are almost achieved at a wide wavelength range from 3.4μm to 4.8μm with the absorptivity over 80%, and the average absorptivity is 93.6%. Meanwhile, the perfect absorptions appear at the wavelengths of 3.6μm, 4μm and 4.4μm. Comparing with the other reported detectors based on black materials and multilayer resonant cavities, this metamaterial absorber has a high absorptivity as well as a wide bandwidth, facilitating the maximum responsivity of single thermocouple as high as 0.89V/W. This hybrid thermocouple is able to operate at room temperature and has the advantages of angle insensitivity, simple in structure and easy integration, which has good potential applications in mid-infrared detection, sensing and imaging.

Angle-independent wideband metamaterial microwave absorber for C and X band application

Abstract In this article, an angle-independent wideband metamaterial microwave absorber (MMA) for C (4–8 GHz) and X (8–12 GHz) band frequency is presented. The unit cell of the proposed MMA consists of outer and inner structure associated with lumped resistors. The outer structure consists of rectangular split-ring resonator, whereas the inner structure consists of circular split-ring resonator. The structure is made up of three layers, in which top and bottom layers are made up of copper acting as a conducting material. The middle layer is made up of FR-4 acting as a dielectric substrate. The resonating structure at the top is designed in such a way that wideband absorption is achieved in the range from 6.11 to 13.52 GHz. The wideband absorption within the range approaches almost unity having a bandwidth of 7.41 GHz. Three different peaks are considered in the range of interest having maximum absorption of 0.94, 0.94, and 0.99 at frequencies of 6.76, 11.15, and 13.07 GHz, respectively. The structure is analyzed with respect to the effective parameters, i.e., effective permittivity ( ${\varepsilon _{{\textrm{eff}}}}$ ) and effective permeability ( ${\mu _{{\textrm{eff}}}}$ ), to prove that the structure acts as a metamaterial. Electric field and current distribution are plotted at three different peaks to prove the mechanism of wideband absorption. Normal and oblique incidence are plotted to determine that the structure is behaving as an angle independent. The simulated structure is fabricated on FR-4 substrate and measured inside an anechoic chamber. Finally, to prove the novelty of the work, the proposed structure is compared with the already reported MMA. The proposed MMA finds practical applications in radar cross section reduction, terrestrial communication, keyless entry system, space communication, radar, and baby monitor.

Polarization-insensitive and wide-angle absorber operating in the visible and near-infrared regimes

This paper investigates a wideband metamaterial absorber (MMA) operating in visible and near-infrared regimes of electromagnetic spectra. The top metasurface of the proposed absorber is made of periodic cube-shaped rods made up of nickel metal and silicon dioxide. The wideband absorption of greater than 80% is achieved when operating from 400 to 1000 nm for normal incidence of light. The results show that the absorption of the absorber is due to the electric resonance of the MMA. Moreover, it was noticed that the polarization-insensitive nature of the MMA is due to the four-folded symmetry of the top Ni-SiO2 cube rods. The absorption was analyzed for the obliquity of the incidence of light. Besides that, the absorber shows large angular stability to the incidence light. The proposed absorber would be practical for solar heating and solar power generation, which can be used in light-based absorption applications.

A Near-Perfect Wideband Metamaterial Absorber Using Conductive Ink with Wide Angular Stability and Polarization Insensitive Behaviour

The work presents a systematic approach to designing and developing a metamaterial-based ultra-wideband absorber with a prime focus on attaining more than 99% absorption for ultra-wideband covering a bandwidth of 8.23 GHz from 11.17 to 19.40 GHz. However, the proposed absorber achieves more than 95% absorption from 9.77 to 20.87 GHz, covering a bandwidth of 11.10 GHz. The structure provides a full-width half-maximum of 17.68 GHz from 6.67 to 24.35 GHz. The proposed absorber demonstrating polarization-insensitive behaviour and broad incident angle stability affirm that the proposed absorber stands up for incorporation in practical applications.

Design of wideband metamaterial absorber using circuit theory for X‐band applications

AbstractA broadband metamaterial absorber working in the X‐band is designed and fabricated by 3D printing in this study. This structure is capable of nearly absorbing the power of incoming waves (more than 90%) in the frequency band starting from 7.1 to 13.8 GHz. This metamaterial absorber is designed based on an infinite array of conductive ribbons, and the thickness of the absorber is just 0.1λ for the minimum frequency (without considering the thickness of the ground layer). A circuit model and transmission line theory are used to design and explain the absorption principle of the proposed structure. Our novel design method is flexible and can be applied to other frequency bands. The satisfaction of the proposed absorber can be applied to many applications namely communication, electromagnetic shielding, radar and satellite. Furthermore, due to the flexibility of the substrate, the proposed absorber is also suitable for flexible applications in the X‐band.

A transparent water-based metamaterial broadband absorber with a tunable absorption band

In this study, a tunable and optically transparent water-based wideband metamaterial absorber (MMA) is proposed and verified. By adjusting the thickness of the water layer, the conversion of the absorber absorption band from 7.4–22.4 GHz to 23.1–35.5 GHz can be achieved, which demonstrates the flexibility of MMA. Indium tin oxide (ITO) as the resonant and reflective layers of the material structure. Optically transparent polymethyl methacrylate (PMMA) is used as a medium container to encapsulate the water. Furthermore, the suggested MMA is polarization insensitive and has broad incident angle stability. Experiments verify the excellent properties of the proposed MMA. As a result, the suggested MMA has various applications in military and medical equipment optical windows.

A high absorptance wide-band metamaterial absorber with metasurface and low-permittivity dielectric slabs

In this paper, a new wide-band and high-absorption metamaterial absorber (WHMA), consisting of a metasurface (MS), three low-permittivity dielectric slabs, and a metal backplane, is proposed and fabricated. The unit cell of MS is concentric rings loaded with chip resistors. This structure exhibits excellent absorption property and improved stability of oblique incidence, which are difficult to be achieved in previous radar absorbing materials. The functions of MS and different dielectric slabs are analysed. At normal incidence, the simulated results indicate that −10 dB absorption and −20 dB absorption bands cover a bandwidth of 4.8–14.3 GHz and 5.70–13.57 GHz, respectively. The measured results show that −10 dB and −20 dB absorption are achieved with the bandwidth of 4.6–16.3 GHz and 5.5–14.4 GHz respectively at normal incidence; below 50° angle of oblique incidence, WHMA can still have wide-band −10 dB absorption. The agreement between simulation and measurement validates the proposed design. Finally, since the structure is made of foam and thin dielectric layers, the area density is relatively low.

Effects of bending on the electro-optical properties of a wide-band silicon-carbon nanotube-based metamaterial absorber

Metamaterials possess superior material properties that make them popular in various applications. They are commonly used in energy, medical, and military fields. Metamaterial absorbers are introduced in order to utilize them in harvesting solar energy. In this article, a novel wide-band Silicon-Carbon Nanotube (Si-CNT) based metamaterial absorber is proposed, and the effects of mechanical loading on electro-optical properties are investigated. The study is conducted within the visible and ultraviolet frequency ranges (400–1200 THz). Concave and convex bending deformations are applied to the absorber within the mentioned frequency range. The results reveal that wide-band absorption rates are achieved for the proposed absorber with a minimum rate of 91.17 % at 400.3 THz. The proposed absorber is found to be polarization-independent and showed high absorption rates up to 45° incident angle within the mentioned frequency range. The absorption rates are observed to increase and shift due to bending deformations. The mechanical stresses formed are also predicted to be below the estimated yield strength, ensuring the structural integrity of the absorber.

Polarization-dependent wideband metamaterial absorber for ultraviolet to near-infrared spectral range applications.

The need for wideband metamaterial absorbers (WBMA) for applications other than sensing and filtering has demanded modifications to the conventional three-layer metal-insulator-metal (MIM) absorber configuration. This modification often results in complex geometries and an increased number of layers requiring complex lithographic processes for fabrication. Here, we show that a metamaterial absorber with rectangular geometry in the simple MIM configuration can provide wideband absorption covering the ultraviolet and near-infrared spectral range. Due to its asymmetric nature, the WBMA is sensitive to the polarization of the incident light and independent of the angle of incidence up to about 45° depending on the polarization of the incident light. The characteristics of the WBMA presented here may be useful for applications such as detectors for wide spectral band applications.

A Wideband and Ultra-Thin Metamaterial Absorber Based on Resistive FSS

A wideband, ultra-thin, wide-angle and polarization-insensitive metamaterial absorber with a single-layer resistive frequency selective surface (FSS) is proposed. The simulated results show that the absorption rate of the absorber is greater than 90% in a frequency range of 24.1–42.6 GHz, and the relative absorption bandwidth is up to 55.47%. The thickness of the structure is 1.2 mm, which is 0.088 λ and 0.156 λ for the lowest and highest frequencies, respectively. The power loss density is analyzed to explore the mechanism of the absorption and the resistive film layer is important for the wideband absorption. Meanwhile, a strong absorption for oblique incidence with wide angle and the characteristics of polarization insensitivity are achieved for the proposed design.

Design and analysis of a wideband and wide angle 3D metamaterial absorber

In this paper, we proposed a three-dimensional (3D) metamaterial absorber joint by lightweight 3D grid structure and traditional magnetic materials, which can achieve wideband and wide-angle perfect absorption at 5–20 GHz. By simulation, the broadband absorption remained almost 90% from 0° to 80° for TM wave. The surface current and power loss distributions were investigated to interpret the physical mechanism of wideband and wide-angle absorption. The broadband and wide-angle absorption were derived from magnetic and electric resonances between the top resistive film, background plane and magnetic loss of magnetic materials. The results proved that different layers of the proposed absorber play different loss roles, and finally contributed to the wideband and wide-angle absorption. The polarization insensitive stability of the proposed absorber was also demonstrated at different polarized angles. The present study provided a new design to achieve a polarization insensitive, wideband and wide-angle absorber. Moreover, the structure absorber has potential applications in other fields, including the solar cell, imaging and detection etc.