Multi-band Metamaterial Absorber Research Articles

Ultra-Thin Multi-Band Polarization-Insensitive Microwave Metamaterial Absorber Based on Multiple-Order Responses Using a Single Resonator Structure.

We design an ultra-thin multi-band polarization-insensitive metamaterial absorber (MMA) using a single circular sector resonator (CSR) structure in the microwave region. Simulated results show that the proposed MMA has three distinctive absorption peaks at 3.35 GHz, 8.65 GHz, and 12.44 GHz, with absorbance of 98.8%, 99.7%, and 98.3%, respectively, which agree well with an experiment. Simulated surface current distributions of the unit-cell structure reveal that the triple-band absorption mainly originates from multiple-harmonic magnetic resonance. The proposed triple-band MMA can remain at a high absorption level for all polarization of both transverse-electric (TE) and transverse-magnetic (TM) modes under normal incidence. Moreover, by further optimizing the geometric parameters of the CSRs, four-band and five-band MMAs can also be obtained. Thus, our design will have potential application in detection, sensing, and stealth technology.

Multi-band metamaterial absorber with arbitrary polarization and wide-incident angle

We propose a multi-band metamaterial perfect absorber with a deep-subwavelength thickness and near-unity absorption coefficient at microwave frequencies. This planar metamaterial is composed of periodically arranged concentric metallic rings and a continuous metallic ground plate separated by one or two lossy dielectric layers. The origin of the induced multi-band perfect absorption is attributed to the multiple impedance-matching to free space and can be achieved through tuning the effective constitutive relations by interactions of several electromagnetic resonances. Numerical simulations reveal the electric field and surface current distributions at each absorption peak, and further analysis indicates that the absorption mainly arises from the dielectric loss. Moreover, the absorption could be enhanced and broaden by overlapping the modes of different rings. The absorption is identical for arbitrary polarizations due to the rotational symmetry of the subwavelength unit. It also remains over 90% energy absorption for a wide angle of incidence up to 45 $$^\circ$$ , which is confirmed by the experiment. The designed multi-band absorber is also easy to manufacture by the mature printed circuit board technology, which is favorable for a wide variety of applications.

Design of multiband selective near-perfect metamaterial absorbers with SiO2 cylinder/rectangle shell horizontally embedded in opaque silver substrate

In this paper, we presented two multiband selective near-perfect absorbers, respectively made of one-dimensional periodic SiO2 cylinder shell and SiO2 rectangle shell arrays horizontally embedded in silver substrate. The spectral-directional absorptivity of the proposed structures was numerically investigated with the finite element based Comsol Multiphysics software. Five near-perfect absorption bands in the wavenumber range from 2500 to 20,000cm−1 for TM-wave incidence were obtained for both absorbers. Physical mechanisms responsible for the multiband absorption were elucidated as due to resonance of magnetic polaritons and the effect of Wood’s anomaly. Furthermore, the effects of polarization angle and geometric parameters on the multiband selective absorption were explored. This work may provide new guidelines for designing high efficient multiband photodetectors or photon sorters.

Multi-band metamaterial absorber topology for infrared frequency regime

In this paper, a new multiband metamaterial absorber design is proposed and the numerical characterization is carried out. The design is composed of three layers with differently sized quadruplets in which the interaction among them causes the multiband absorption response in the infrared frequency regime. In order to characterize the absorber and explain the multiband topology, some parametric studies with respect to the dimensions of the structure are carried out and the contributions of the quadruplets to the absorption spectrum are analyzed. According to the results, it is found that the proposed metamaterial absorber has five bands in the infrared frequency regime with the absorption levels of: 98.90%, 99.39%, 86.46%, 92.80% and 97.96%. Moreover, the polarization dependency of the structure is examined and it is found that the design operates well as a perfect absorber with polarization independency in the studied frequency range.

Creating a Multiband Perfect Metamaterial Absorber at K Frequency Band Using Defects in the Structure

We present a simple method to achieve a multiband perfect metamaterial absorber for use in the K band by applying defects to the absorber structure. Open boundary conditions with an excitation port are used for simulation of the whole considered structure. A defect was then introduced into the structure to obtain multiband absorption. Two perfect absorption peaks were observed at 19.8 GHz and 23.1 GHz for the structure with a defect of 2 × 2 unit cells. The multiple resonance frequencies could be tuned by varying the defect dimensions. In addition, it was found that the absorber structure is insensitive to the polarization angle of the incident electromagnetic wave over a wide range due to the symmetry of the configuration. This represents a simpler method to create a multifrequency absorber compared with previous works. To the best of our knowledge, this is the first study considering the influence of structural defects on the absorption frequencies of a metamaterial absorber.

Single-Patterned Metamaterial Structure Enabling Multi-band Perfect Absorption

Multi-band or broadband perfect metamaterial absorbers, based on coplanar super-unit structure or multiple vertically stacked layers, have received intense attention because of their potential for practical applications. The resonance mechanism of them usually only utilizes the overlapping of the fundamental resonance of the different-sized patterns, and neglects the high-order resonance of the structure, and thus making the proposed structures quite troublesome to be fabricated and the mechanism of the current demonstrated absorbers lack of novelty. In this paper, a simple design of dual-band terahertz absorber consisted of only a traditional square metallic patch and a dielectric layer on top of a continuous ground plane is presented. Simulation results show that the single resonant structure has two resonance absorption peaks, which are both average over 99.5 %. The mechanism of the dual-band absorber is due to the overlapping of the fundamental mode and three-order response of the patterned structure, which is totally different from previous reports that only combining the fundamental resonances of the different-shaped complex structures to obtain the dual-band response. Furthermore, the proposed single-patterned structure can be used to extend the number of the absorption peaks (for example, triple-band absorber) by combining one more resonance (the five-order response). The proposed absorbers with the simple structure design have potential applications in many areas, such as detection, sensing, and selective thermal emitters.

Multi-band polarization independent cylindrical metamaterial absorber and sensor application

A multi-band perfect metamaterial absorber (MA) based on a cylindrical waveguide with polarization independency is numerically presented and investigated in detail. The proposed absorber has a very simple configuration, and it operates at flexible frequency ranges within the microwave frequency regime by simply tuning the dimensions of the structure. The maximum absorption values are obtained as 99.9%, 97.5%, 85.8%, 68.2% and 40.2% at the frequencies of 1.34 GHz, 2.15 GHz, 3.2 GHz, 4.31 GHz and 5.41 GHz, respectively. The numerical studies verify that the proposed model can provide multi-band perfect absorptions at wide polarization and incident angles due to its rotational symmetry feature. We have also realized sensor and parametric study applications in order to show additional features of the suggested model. The suggested MA enables myriad potential applications in medical technologies, sensors and in defense industry etc.

Intensity-modulating graphene metamaterial for multiband terahertz absorption.

In this paper, we design a tunable strength multiband absorber consisting of a graphene metamaterial structure and a thick dielectric interlayer deposited on a metal ground plane. We investigate the tunable conductivity properties of the graphene metamaterial and demonstrate multiband absorbers with three absorption bands using a polyimide interlayer in the 0-2.25 THz range by numerical simulation. The results show that the mix absorptivity reached 99.8% at 1.99 THz, and the absorptive strength can be tuned with the modulation depth up to 84.2%. We present a theoretical interpretation based on a standing wave field, which shows that the field energy is localized inside the thicker spacer and then dissipated, effectively trapping the light in the metamaterial absorbers with negligible near-field interactions. The standing wave field theory developed here explains all the features of the multiband metamaterial absorbers and provides a profound understanding of the underlying physics.

Design of a multiband terahertz perfect absorber**Project supported by the National Natural Science Foundation of China (Grant No. 11504006), the Key Scientific Research Project of Higher Education of Henan Province, China (Grant No. 15A140002), and the Science and Technology Planning Project of Henan Province, China (Grant No. 142300410366).

A thin-flexible multiband terahertz metamaterial absorber (MA) has been investigated. Each unit cell of the MA consists of a simple metal structure, which includes the top metal resonator ring and the bottom metallic ground plane, separated by a thin-flexible dielectric spacer. Finite-difference time domain simulation indicates that this MA can achieve over 99% absorption at frequencies of 1.50 THz, 3.33 THz, and 5.40 THz by properly assembling the sandwiched structure. However, because of its asymmetric structure, the MA is polarization-sensitive and can tune the absorptivity of the second absorption peak by changing the incident polarization angle. The effect of the error of the structural parameters on the absorption efficiency is also carefully analyzed in detail to guide the fabrication. Moreover, the proposed MA exhibits high refractive-index sensing sensitivity, which has potential applications in multi-wavelength sensing in the terahertz region.

Multiband Metamaterial Absorber Design Based on Plasmonic Resonances for Solar Energy Harvesting

A new metamaterial absorber is designed and characterized numerically for the harvesting of solar energy. The design is composed of three layers in which the interaction among them gives rise to the plasmonic resonances. The main operation frequency range of the proposed structure is chosen to be the visible regime. However, the design is also analyzed for the infrared and ultraviolet regimes. In order to characterize the absorber, some parametric studies with respect to the dimensions of the structure are carried out. According to the results, it is found that the proposed metamaterial absorber has 98.2 % absorption capability at 445.85 THz and 99.4 % absorption capability between 624 and 658.3 THz. Moreover, the polarization dependency of the structure is examined and it is found that the design operates well as a perfect absorber with polarization independency for the studied frequency range. As a result, the proposed metamaterial absorber can be used for solar energy harvesting as it provides multiple perfect absorption bands in the visible regime.

Compact multi‐band polarisation‐insensitive metamaterial absorber

In this study, a novel multi-band metamaterial absorber has been proposed which is ultra-thin, compact, polarisation-insensitive and wide-angle absorptive. The proposed structure comprises two concentric metallic rings printed on a dielectric substrate which is backed by a metal ground plane. The proposed structure exhibits four distinct absorption peaks at 4.11, 7.91, 10.13 and 11.51 GHz with peak absorptivities of 98.81, 99.68, 99.98 and 99.34%, respectively, under normal incidence. The designed absorber is polarisation insensitive due to four-fold symmetry, which has been confirmed by simulation and measurement studies. Moreover, the structure shows high absorption (over 90%) for oblique incident angles up to 45° for both transverse-electric and transverse-magnetic polarisations. The surface current distributions at the four absorption frequencies have been illustrated to explain the absorption mechanism of the structure. In addition, several parametric variations are performed to observe the effects of the geometrical dimensions on the absorption performance. The free space measurement method has been utilised to measure the responses of the fabricated structure, which are in good agreement with the simulated results. The proposed ultra-thin (∼0.013λ0 thin corresponding to lowest absorption frequency) absorber is anticipated to be useful in various potential applications like stealth technology, electromagnetic interference, electromagnetic compatibility and wireless communication.

Multi-band polarization insensitive metamaterial absorber with dual cross-wires structure

A five-band metamaterial absorber (MMA) based on a simple planar structure is proposed. It utilizes different areas of a single unit cell to match impedance, and produces different absorptive frequencies. Numerical calculation shows that the MMA has five different absorption peaks at 3.78 GHz, 7.66 GHz, 10.9 GHz, 14.5 GHz and 16.7 GHz, and their absorption rates reach 95.5%, 98.6%, 95.7%, 96.6% and 99.8%, respectively. The proposed structure is polarization insensitive for transverse electric (TE) and transverse magnetic (TM) incident waves. Also, the absorptive characteristics over large incident angles are examined. In addition, we analyze the absorption mechanism by the surface current density and power flow density distributions. This simple structure provides a way to design multi-band MMA, and also saves the cost of fabrication.

Ultra-compact metamaterial absorber for multiband light absorption at mid-infrared frequencies

We investigated a multiband metamaterial absorber composed of one-side open cavities. A metallic sidewall effectively prevents destructive coupling between the neighboring cavities. Thus, the number of subunits in one period, which determines the number of multibands or the width of broadband, can be greatly increased. A redshift effect of the resonances is observed theoretically and numerically when the distance between the subunits is reduced. Although the separation is very small and the coupling between the neighboring cavities is strong, the angular insensitivity of the absorption is well-maintained over a wide range. Our findings may enable applications of ultra-compact multiband sensors and thermal emitters.

Graphene metamaterial for multiband and broadband terahertz absorber

In this paper, we present the efficient design of functional graphene thin film metamaterial on a metal-plane separated by a thick dielectric layer. Perfect absorption is characterized by the complete suppression of incident and reflected light and complete dissipation of incident energy. We investigate the properties of graphene metamaterials and demonstrate multiband absorbers that have five absorption bands, using silicon interlayers, in the 0–2.2THz range. The absorption rate reached up to 99.9% at a frequency of 1.08THz, and the quality factor was 6.98 for a 0.14THz bandwidth. We present a novel theoretical interpretation based on standing wave field theory, which shows that coherent superposition of the incident and reflection rays produce stationary waves, and the field energy localized inside the thick spacers and dissipated through the metal-planes. Thus, light was effectively trapped in the metamaterial absorbers with negligible near-field interactions, causing high absorption. The theory developed here explains all features observed in multiband metamaterial absorbers and therefore provides a profound understanding of the underlying physical mechanisms.

Design, synthesis, characterization and performance evaluation of multi-band perfect metamaterial absorber

This paper presents the design, synthesis, characterization, and performance evaluation of a metamaterial absorber having four distinct absorption peaks. The proposed absorber is based on the periodic array of the hexagonal closed rings and octa-star structure printed over the dielectric substrate. The dimensions of unit cell are optimized such that the absorption takes place at the distinct frequency near the Federal Communications Commission defined radar spectrum e.g. at 4.10, 6.15, 10.05, and 15.52 GHz with the absorptivity of 0.98, 0.99, 0.99, and 0.99, respectively. The proposed structure is fabricated and the experimental result shows high absorptivity under transverse electric and magnetic polarization for the wide angle of incidence angles, which is in concurrence with the simulated results. The equivalent circuit model of the absorber has been developed sequentially for each of the structure. Furthermore, the complex refractive index of the metamaterial structure has been retrieved in order to have a detailed analysis, which supports the absorption phenomena at all the corresponding frequencies. The proposed metamaterial structure appears to be a potential candidate for absorber applications in the radar cross-section reduction, thermal detectors, and thermal imaging.

Design of a tunable multiband terahertz waves absorber

A thermally tunable multiband terahertz metamaterial absorber comprising a periodic array of closed metallic square ring resonators and four metal bars parallel to the four side of the square ring, fabricated on the low-temperature co-fired ceramic (LTCC) strontium titanate (STO) dielectric layer dielectric substrate has been proposed. The resonance frequencies of the absorber are demonstrated to be continuously tuned in the terahertz regime by increasing the temperature. It is found that in the window between 0.05 and 0.35 THz the absorber has three distinctive absorption peaks at frequencies 0.129 THz, 0.198 THz and 0.316 THz (at the room temperature), whose peaks are attained 99.3%, 99.1% and 94.6% respectively. The tunability is attributed to the temperature-dependent permittivity of the substrate and attained to 67.3% frequency tuning depth at the room temperature, when the temperature varied from 400 K to 200 K. The proposed designs ensure broadband thermally tunable terahertz devices.

Polarization angle independent perfect multiband metamaterial absorber and energy harvesting application

A new kind of multi-band metamaterial absorber based on the concentric ring resonators is engineered to be used in various microwave applications including energy harvesting. Numerical investigations are carried out step by step for observation of the effect of each ring resonator. The results reveal that the structure almost perfectly absorbs the electromagnetic wave with polarization angle independency at multiple resonant frequencies in the microwave range. Additionally, the structure is characterized according to the dimension and geometry variations. For the harvesting application, three different efficiencies are suggested, discussed, and calculated in terms of their contribution to the conditional realization of the connection between the absorption characteristics of the material and its energy harvesting functionality. Also the multi-band absorption characteristics of no-load conditions are presented and compared with the loading conditions through the energy harvesting. As a result, 50 % of the incoming wave energy whose correspondence is 0.25 W is converted to real power through the resistive loads at 5.88 GHz.

Polarization-insensitive wide-angle multiband metamaterial absorber with a double-layer modified electric ring resonator array

In this letter, we report the design, demonstration and discussion of a multi- and broad- band metamaterial absorber (MMA) with wide angle polarization insensitive at microwave region. The MMA consisting of double layered electric ring resonator (ERR) with four fold rotational symmetry structure is used to realize a desirable absorption. Strong triple absorption peaks in 2∼8 GHz and broadband microwave absorption in 10∼18 GHz are demonstrated. The absorption can be reached as high as 0.73, 0.73 and 0.94 at 4.41, 5.15, 6.37 GHz, respectively. The multiband absorbing features originate from the synergetic effects of dipole resonance and Fabry-Pérot interference between two or three metasurfaces. This design is of high practical for constructing broad band and multiband absorber for electromagnetic intereference/compatibility (EMI/EMC) applications.

Independent polarization and multi-band THz absorber base on Jerusalem cross

In this paper, we present the design and simulation of a single and multi-band perfect metamaterial absorber (MA) in the THz region base on Jerusalem cross (JC) and metamaterial load in unit cells. The structures consist of dual metallic layers for allowing near-perfect absorption with absorption peak of more than 99%. In this novel design, four-different shape of Jerusalem cross is presented and by adding L, U and W shape loaded to first structure, we tried to achieve a dual-band absorber. In addition, by good implementation of these loaded, we are able to control the absorption resonance at second resonance at 0.9, 0.7 and 0.85THz respectively. In the other hand, we achieved a semi stable designing at first resonance between 0.53 and 0.58THz. The proposed absorber has broadband polarization angle. The surface current modeled and proved the broadband polarization angle at prototype MA. The LC resonance of the metamaterial for Jerusalem cross and modified structures are extracting from equivalent circuit. As a result, proposed MA is useful for THz medical imaging and communication systems and the dual-band absorber has applications in many scientific and technological areas.

Achieving a multi-band metamaterial perfect absorber via a hexagonal ring dielectric resonator**Project supported by the National Natural Science Foundation of China (Grant Nos. 61331005, 11204378, 11274389, 11304393, and 61302023), the Aviation Science Foundation of China (Grant Nos. 20132796018 and 20123196015), the Natural Science Foundation for Post-Doctoral Scientists of China (Grant Nos. 2013M532131 and 2013M532221), the Natural Science Foundation of Shaanxi

A multi-band absorber composed of high-permittivity hexagonal ring dielectric resonators and a metallic ground plate is designed in the microwave band. Near-unity absorptions around 9.785 GHz, 11.525 GHz, and 12.37 GHz are observed for this metamaterial absorber. The dielectric hexagonal ring resonator is made of microwave ceramics with high permittivity and low loss. The mechanism for the near-unity absorption is investigated via the dielectric resonator theory. It is found that the absorption results from electric and magnetic resonances where enhanced electromagnetic fields are excited inside the dielectric resonator. In addition, the resonance modes of the hexagonal resonator are similar to those of standard rectangle resonators and can be used for analyzing hexagonal absorbers. Our work provides a new research method as well as a solid foundation for designing and analyzing dielectric metamaterial absorbers with complex shapes.