Dual-band Metamaterial Absorber Research Articles

Design and analysis of K and Ku-band wide-angle polarization-insensitive dual-band perfect metamaterial absorber

This paper presents a polarization-insensitive dual-band metamaterial perfect absorber applied to the Ku and K bands. The proposed dual-band metamaterial absorber (MMA) is a three-layer structure of metal-dielectric-metal. The top metal layer consists of a split circle ring, two intersecting square rings, and a circle ring, the bottom metal layer is made of copper, and the middle dielectric layer is made of FR-4. The simulation results show that the MMA has two absorption peaks at frequencies of 12.06 GHz and 19.07 GHz, with absorption rates of 99.95% and 99.73%, respectively. The MMA exhibits good polarization insensitivity in TE and TM modes. In TE mode, the increase in incident angle significantly broadens the absorption bandwidth. The experimental results verified the dual-band perfect absorption of MMA and the incident angle gain characteristic of TE mode. The proposed dual-band MMA can be applied in related fields such as radar antennas, satellite communication, and sensing.

Dual-band InSb metamaterial absorber based on temperature and magnetic field control

Dual-band InSb metamaterial absorber based on temperature and magnetic field control

Dual-band flexible metamaterial absorber working in 5G band

Dual-band flexible metamaterial absorber working in 5G band

Compact dual-band metamaterial absorber: Enhancing electromagnetic energy harvesting with polarization-insensitive and wide-angle capabilities

A novel compact metamaterial (MM) energy harvester optimized for Wi-Fi frequencies (2.4 GHz and 5.8 GHz) is introduced in this study. The energy harvester exhibits polarization insensitivity and versatility across various incident angles. The energy harvesting (EH) efficiency is evaluated using numerical simulations and practical experiments. The design features ring and octagonal resonators constructed with Rogers RT 5880 Substrate, with each octagonal resonator incorporating a strategically placed gap for lumped elements. The structure's impedance is meticulously aligned with free space to efficiently absorb incident electromagnetic (EM) power with minimal reflection. The simulation outcomes indicate that normal incidence at 2.4 GHz and 5.8 GHz yields high-efficiency levels of 96 % and 98 %, respectively. To validate these results experimentally, we conducted tests in an anechoic chamber using a fabricated 3 × 3 array structure. The results showed a significant correlation between the simulation outcomes and experimental data. The proposed MM energy harvester is highly efficient and shows great promise as an alternative for various microwave applications, such as EH and wireless power transfer.

Optically Transparent Dual-Band Metamaterial Absorber Using Ag Nanowire Screen-Printed Second-Order Cross-Fractal Structures

In this paper, we propose an optically transparent dual-band metamaterial absorber (MMA) that uses Ag nanowire screen-printed fractal structures. The proposed MMA exhibits near-perfect absorption in the C- and K-bands. This dual-band absorption property is achieved through two inductive–capacitive (L-C) resonances located at 6.45 and 21.14 GHz, which are generated by the second-order fractal structures. We analyzed the microwave absorbing mechanisms through the distributions of the surface current and electromagnetic field on the top and bottom layers. The MMA demonstrates an optical transmittance of 63.1% at a wavelength of 550 nm. This high optical transmittance is attained by screen printing transparent Ag nanowire ink onto a transparent PET substrate. Since screen printing is a simple and low-cost fabrication method, the proposed MMA offers the advantages of being low cost while having the properties of optical transparency and effective dual-band absorption. Consequently, it holds great potential for the radar stealth application of C- and K-bands in that it can be attached to the windows of stealth aircraft due to its optical transparency and dual-band near-perfect absorption property.

Polarization-Angle-Insensitive Dual-Band Perfect Metamaterial Absorbers in the Visible Region: A Theoretical Study

Metamaterial absorbers have been studied extensively due to their potential applications in the field of photonics. In this paper, we propose a simulation study of a polarization-angle-insensitive dual-band perfect metamaterial absorber with absorption peaks at 654 and 781 nm, respectively. By adjusting the structure parameters, dielectric thickness, and refractive index, the obtained absorber has high scalability in the visible wavelength region. To further understand the performance of the cross-structure absorber, analysis of its electric and magnetic field distribution shows that it produces two resonance modes leading to different absorption properties. In addition, the position and intensity of the absorption peaks were found to be unchanged with increasing incident polarization angle, indicating that the absorber is insensitive to the polarization of the incident light. The absorber has great flexibility and has good application potential in sensing and detection.

Design and Development of Metamaterial Absorber for IoT Applications

Microwave absorbers are efficient design structures that enhance electromagnetic shielding and reduce electromagnetic wave interference. It dissipates an incident electromagnetic wave by converting it into other forms of energy, thereby preventing the electromagnetic wave's reflection and/or transmission. A novel electromagnetic metamaterial dual-band microwave metamaterial absorber for IoT application is proposed in this manuscript. The proposed absorber has an excellent absorption rate, above 98% and 99% at 2.4 and 5.1 GHz, respectively. The structure, designed over FR-4 material, provides negative permittivity and permeability. The Nicolson Ross Weir (NRW) method investigates metamaterial properties. An array of (3 × 3) unit cell absorbers is designed, developed, and tested; simulated and measured results are in good agreement.

Dual-Band Metamaterial Microwave Absorber using Ring and Circular Patch with Slits

This paper proposes a dual-band metamaterial microwave absorber operating at 2.5 GHz and 5.8 GHz. The absorber consists of a ring and a circular patch with slits resonator structures printed on a FR4 dielectric substrate backed by a ground layer. The main advantage of the absorber lies in its design flexibility in which each absorption band is independent and can be individually tuned by changing the dimensions of each resonator structure. The absorber unit cell is simulated and parametrically optimized using Computer Simulation Technology (CST) software. The absorption mechanism is analyzed through surface current analysis. The absorber prototype, with dimensions of 200 × 200 × 1.6 mm3 and consisting of an array of 7 × 7 unit cells, is fabricated and experimentally investigated using antennas in free-space measurement. The absorber exhibits over 97% absorption at both resonance frequencies. Furthermore, the absorber is demonstrated to be applicable in sensing applications for dielectric constant determination. With its design simplicity, wide-angle receptive, and polarization insensitive behavior, it is envisaged that the proposed absorber will find practical use in absorbing and sensing applications.

A Dual Band 28/38 GHz Metamaterial Absorber for 5G Applications

A dual-band metamaterial absorber (MMA) for fifth-generation (5G) applications is discussed in this work. The suggested absorber works at frequency bands of 28 GHz and 38 GHz. The suggested MMA unit cell with a size of 5.8 mm × 5.8 mm (0.54 λ0 × 0.54 λ0 at 28 GHz) is designed on 1.5 mm (0.14 λ0) low-cost FR4 substrate and composed of two metallic ring resonators. The suggested MMA is investigated to validate its performance for different polarization for transverse electric (TE) and transverse magnetic (TM). Both normal and oblique angles are studied. The MMA has a simple structure with a compact size. Different parameters such as the currents, electric field distributions, and normalized impedance are studied. The array of 10 × 10 unit cells is utilized to verify the simulated outcomes. The suggested MMA is fabricated and tested, and its outcomes are compared to the simulated outcomes. The MMA is operated at dual bands 28/38 GHz with high absorption rates of 98 and 98.4%, respectively, under the normal incidence for both outcomes. A good matching between the two outcomes is observed, which supports the MMA for 5G applications.

MXene fractal-based dual-band metamaterial absorber in the visible and near-infrared regime

MXene fractal-based dual-band metamaterial absorber in the visible and near-infrared regime

Dual-band complementary metamaterial perfect absorber for multispectral molecular sensing.

Metamaterial perfect absorbers (MPAs) show great potential in achieving exceptional sensing performance, particularly in the realm of surface-enhanced infrared absorption (SEIRA) spectroscopy. To this aim, it is highly desirable for the localized hotspots to be readily exposed and accessible to analyte with strong mode confinement to enhance absorption. Here, we propose a quasi-three-dimensional MPA based on cross-shaped coupled complementary plasmonic arrays for highly sensitive refractive index sensing and molecular vibrational sensing. Dual-band perfect absorption can be approached with the two plasmonic resonances corresponding to the electric dipole-like mode of cross antenna array and the magnetic dipole-like mode of cross hole array, respectively. Large portions of the electric field of the hotspots are exposed and concentrated in the gap between the elevated cross antenna and its complementary structure on the substrate, leading to improved sensing sensitivities. An ultrathin polymethyl methacrylate (PMMA) film induces a significant redshift of the magnetic dipole-like mode with an 11.8 nm resonance shift per each nanometer polymer thickness. The value is comparable to the reported sensitivity of single molecule layer sensors. Additionally, the simultaneous detection of the C = O and C-H vibrations of PMMA molecules is enabled with the two plasmonic resonances adjusted by changing the lengths of the two cross branches. Remarkably, the observed mode splitting and anti-crossing behavior imply the strong interaction between plasmonic resonance and molecular vibration. Our dual-band MPA based on coupled complementary plasmonic arrays opens a new avenue for developing highly sensitive sensors for the detection of refractive index and multispectral molecular vibrations.

Dual-Band Terahertz Metamaterial Absorber and Its Refractive-Index-Sensing Application for Material Films

Metamaterial absorbers are an emerging and rapidly growing technology with potential applications in optoelectronics, such as refractive index sensing and energy harvesting. Herein, a dual-band terahertz metamaterial absorber is investigated by exploiting a patch of circular loops and cross-shaped structures. The designed absorber composes of a periodic metallic metasurface and a continuous reflector layer, which are separated by a benzocyclobutene dielectric film. The perfect absorptivity properties of the absorber, revealed at frequencies of 0.6 and 1.2 THz, can be flexibly designed by manipulating the geometrical dimensions. A sample of the designed absorber prototype is manufactured under a microfabrication process and measured through a terahertz time-domain spectrometer in free space. In addition, the potential application of the proposed terahertz absorber in refractive index sensing is analyzed and experimentally verified, which has an excellent unit sensitivity of 0.13 THz/RIU at 0.6 THz and 0.27 THz/RIU at 1.2 THz, respectively. The practicability in sensing applications is verified by coating polyimide and poly(dimethylsiloxane) dielectric films on the surface of the absorber, and the absorption frequency shifts at 1.2 THz are practically coincident with the simulated ones. This proposed prototype is an effective manner for terahertz metamaterial absorbers with potential applications in the sensor field.

A high Q-factor dual-band terahertz metamaterial absorber and its sensing characteristics.

In this paper, a dual-band metamaterial absorber in the terahertz frequencies is proposed and its refractive index sensing characteristics is analyzed. The metamaterial structure is designed using a square metal ring with four T-shaped strips loaded outside of the ring, where the metal periodic array is on top of a silicon wafer backed with a metal ground plane. The resonant frequencies of the absorber are at 0.89 and 1.36 THz, whose absorption rates are both over 99% under normal TE and TM polarized incidences. The full widths at half maximum of them are 4.4 and 11.2 GHz, respectively, resulting in high quality factors (Q-factors) for these two frequency bands. The absorption rate of the absorber remains stable as the incident and polarized angles are changed. Several proposed metamaterial absorbers are experimentally fabricated and electron beam lithography (EBL) technology is employed. Good measurement results of the dual-band absorption performance are obtained using a terahertz time-domain spectroscopy system based on photoconductive antennas. Furthermore, the metamaterial absorber also shows sensing properties for analytes with different refractive indices or thicknesses. This work provides a new choice for the design of high-Q dual-band terahertz metamaterial absorbers and their application to refractive index sensing.

Tunable and three-dimensional dual-band metamaterial absorber based on electromagnetically induced transparency with vanadium dioxide.

A tunable and three-dimensional dual-band metamaterial absorber based on electromagnetically induced transparency (EIT) is proposed. The unit cell of the metamaterial absorber consisted of a cut wire (CW), two split ring resonators (SRRs), a metal plate and a patterned vanadium dioxide (VO2) film. The two absorption peaks could be dynamically controlled by tuning the conductivity of VO2 with the maximum absorptions of 97.5% at 1.05 THz and 96.5% at 1.16 THz. The physical mechanism of the metamaterial absorber was explained by the electric field, magnetic field, power loss density and surface current distributions. In addition, the metamaterial absorber exhibited a wide polarization angle for y-polarization wave and x-polarization wave and showed good robustness against oblique incidence. Moreover, the metamaterial absorber exhibited a high fault tolerance with a variation in the geometric parameters. Our work provides a novel method for the fabrication of multi-band metamaterial absorbers and has promising applications in terahertz sensors, modulators and filters.

Mechanically tunable dual-band metamaterial absorber at ultra-high frequency

We numerically demonstrated a dual-band metamaterial absorber (MPA) operating in low frequency range based on a flexible polyimide substrate. For the flat configuration, two absorption peaks are obtained at 450 MHz and 1.47 GHz with absorption over 90%. The ratios of the periodicity of unit cells and thickness to the longest absorption wavelength are 1/12 and 1/114, respectively. Especially, our MPA is insensitive with polarization and stable with the oblique incidence angle of incoming electromagnetic waves. The proposed MPA maintains an absorption over 90% when incident angle is increased up to 60o. Furthermore, since structure is wrapped and attached to cylindered surfaces (the varying radii from 200 to 500 mm), new absorption peaks can be obtained at higher frequency range. For both flat and curvature states, the absorption mechanism is explained by the magnetic resonance and the perfect impedance matching phenomena.

A Tunable and Wearable Dual-Band Metamaterial Absorber Based on Polyethylene Terephthalate (PET) Substrate for Sensing Applications.

Advanced wireless communication technology claims miniaturized, reconfigurable, highly efficient, and flexible meta-devices for various applications, including conformal implementation, flexible antennas, wearable sensors, etc. Therefore, bearing these challenges in mind, a dual-band flexible metamaterial absorber (MMA) with frequency-reconfigurable characteristics is developed in this research. The geometry of the proposed MMA comprises a square patch surrounded by a square ring, which is mounted over a copper-backed flexible dielectric substrate. The top surface of the MMA is made of silver nanoparticle ink and a middle polyethylene terephthalate (PET) substrate backed by a copper groundsheet. The proposed MMA shows an absorption rate of above 99% at 24 and 35 GHz. In addition, the absorption features are also studied for different oblique incident angles, and it is found that the proposed MMA remains stable for θ = 10-50°. The frequency tunability characteristics are achieved by stimulating the capacitance of the varactor diode, which connects the inner patch with the outer ring. To justify the robustness and conformability of the presented MMA, the absorption features are also studied by bending the MMA over different radii of an arbitrary cylinder. Moreover, a multiple-reflection interference model is developed to justify the simulated and calculated absorption of the proposed MMA. It is found that the simulated and calculated results are in close agreement with each other. This kind of MMA could be useful for dual-band sensing and filtering operations.

A Dual-Band Guided Laser Absorber Based on Plasmonic Resonance and Fabry-Pérot Resonance.

We numerically investigated a dual-band metamaterial absorber based on the combination of plasmonic resonance and Fabry–Pérot (FP) resonance, which can achieve near-unity absorption for guided lasers. The absorber is constructed by a three-layer metal-insulator-metal (MIM) periodic configuration. In each unit cell, there is a gold-silicon cross on a thin silicon layer and a bottom nickel film. Numerical results show that, at normal incidence, the structure strongly absorbs light at wavelengths of 1.064 μm and 10.6 μm, with absorption rates higher than 94%. It is revealed that the two absorption peaks result from FP resonance in the thin silicon layer and plasmonic resonance in the cross, respectively. In addition, the absorber is polarization insensitive and is tolerant to the incident angle. The proposed combination of different resonances has the advantage of easily producing double absorption peaks with very large wavelength differences, and provides a new approach to the design of metamaterial absorbers.

Tuning metallic stub loaded symmetrical resonator based dual band metamaterial absorber for wave shielding from Wi-Fi frequencies

In this article, a simple metamaterial absorber (MMA) is presented aiming absorption of microwave signals from Wi-Fi frequencies of 2.4 GHz, and 5 GHz. The MMA unit cell constructed on 20 × 20 mm2 FR4 substrate provides maximum absorption of 99.2% and 99.9% at 2.4 GHz and 5 GHz with the flexibility of on-design tuning of maximum absorption frequencies. The tuning metallic stubs connected with the outer ring provide the provision of frequency adjustment from 2.34 GHz to 2.45 GHz, whereas middle ring stubs along with the innermost ring assists for frequency tuning from 4.68 GHz to 5.1 GHz. Due to symmetrical structure, excellent angular stability up to 60° is achieved with near zero cross-polarization effect for both transverse electric (TE) and transverse magnetic (TM) modes of excitation. The measured result of the proposed MMA is analyzed that shows good similarity with the simulated one. Due to its simplistic design within nominal dimension, high absorption, flexibility to frequency tuning, wide angular stability, and no cross-polarization effect, this MMA can be a good candidate for absorber applications in wireless communication systems, especially for wave shielding from Wi-Fi frequencies.

A graphene based dual-band metamaterial absorber for TE polarized THz wave

A graphene based tunable metamaterial perfect absorber is designed, which is a classic and simple sandwich structure composed of a non-rotationally symmetric graphene pattern layer, a TOPAS dielectric layer and a thick enough gold ground plane. The dynamically adjustable absorption property of the proposed absorber is polarization sensitive, which is novel compared with the widely studied polarization insensitive metamaterial absorber. For TE polarized incident electromagnetic waves (EMW), the dual-band absorption can be generated at frequencies of 4.268 THz and 6.032 THz with peak absorption coefficients up to 99.99% and 99.79%, respectively. But for TM light, there is only one near unity absorption band located at about 4.148 THz. So it will have potential application value for the polarization state resolution of THz waves. The research mainly concentrates on the dual-band tunable absorption under TE polarized incident light. The factors affecting the absorption properties of the proposed absorber are studied by discussing the dependence of the geometric parameters as well as chemical potential and relaxation time of the graphene on the absorption. The simulation results are verified by using multiple reflection interference theory (MRIT) and impedance matching theory (IMT), and the results show that the theoretical results match well with the simulation results. The absorber can achieve good absorption performance in a wide range of incident angles for TE light. Furthermore, by selecting two different graphene chemical potential, good performance of THz switching can be realized. In addition, the application in the field of refractive sensing is also investigated in detail, and higher sensitivity and better figure of merit (FOM) can be obtained. Thus, the designed graphene-based dual-band THz metamaterial absorber has great potential in polarization resolution, EMW absorbing, THz switching, refractive index sensing and so on.

Dual-band polarization-sensitive terahertz metamaterial absorber possessing frequency and amplitude dynamically-continuously tunable characteristics

In order to suit the increasingly complex electromagnetism environment, multifunctional and continuously tunable terahertz device is becoming a research focus. In this paper, a frequency and amplitude tunable dual-band terahertz metamaterial absorber is proposed. Continuous tuning of absorption frequency and amplitude are completed by dynamic control of the conductivity of photosensitive silicon and the polarization angle, respectively. The tuning range of 55 GHz and amplitude modulation depth up to 100% are obtained. It can be concluded that the structure provides a new approach for the realization of future terahertz metamaterial absorbers possessing the characteristics of multifunction, portability, and intelligence.