Dual-band Metamaterial Absorber Research Articles

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.

Thermally and magnetically controlled dual-band terahertz metamaterial absorber based on InSb

A thermally and magnetically controlled dual-band terahertz metamaterial absorber with a simple structure consisting of a patterned InSb film, a Teflon dielectric layer, and a metal board is designed and investigated. Numerical simulation results demonstrate that the absorption peak can reach 94% at 0.434 THz and 0.692 THz at 300 K, in the absence of an applied magnetic field. The absorber has the features of polarization insensitivity due to the symmetry of the structure and wide incidence angle absorption. The physical absorption mechanism can be analyzed by the impedance matching theory, the electric field distribution, the current distribution, and the excitation of LC resonance theory. Furthermore, the metamaterial absorber enables temperature-tunable characteristics due to the temperature-dependent variation of the permittivity of InSb in the terahertz region. By varying temperature from 295 to 320 K, the first resonance frequency gradually shifts from 0.413 to 0.529 THz with the second peak shifting from 0.654 to 0.863 THz. In addition, frequency dependent absorption of the InSb-based metamaterial absorber under a series of applied magnetic fields is discussed. When the magnetic field B is changed from 0.2 T to 1T, the dual resonant frequencies gradually shift from 0.4816 THz to 0.423 THz and 0.7804 THz to 0.716 THz. The InSb pattern film behaves as a resonant unit, thus providing an alternative method for designing independent bi-tunable absorbers in the terahertz band. The proposed absorber has the advantages of good tunability, simple structure, and high sensitivity, which has great potential in terahertz sensors. This work provides an effective method for implementing thermally and magnetically dual-controlled terahertz metamaterial absorbers.

Dual-Band Terahertz Perfect Absorber Based on Metal Micro-Nano Structure

We propose a sub-wavelength range-based dual-band tunable ideal terahertz metamaterial perfect absorber. The absorber structure consists of three main layers, with the absorber layer consisting of a metal I-shaped structure. By simulating the incident wave absorbance of the structure, we found that the structure has more than 99% absorption peaks in both bands. In addition, we have investigated the relationship between structural absorbance and the structural geometrical parameters. We have studied the relationship between the thickness of the metal absorber layer hb and the absorbance of the metamaterial structure in the 4–14 THz band. Secondly, we have studied the relationship between the thickness of the SiO2 dielectric layer and structural absorbance. Afterwards, we have studied the relationship between the incident angle of the incident electromagnetic wave and structural absorbance. Finally, we have studied the relationship between the length of the metal structure and structural absorbance. The structure can be effectively used for detectors, thermal emitters, terahertz imaging and detection.

A Rectangle-quartet Metamaterial for Dual-band Perfect Absorption in the Visible Region

Based on rectangle-shaped structures, we create a dual-band metamaterial perfect absorber (DMPA) in the optical region. The independent-polarization absorption is a significant advantage as well as the simple integrated progress for constituent materials. In particular, absorption can be obtained to be over 90% in a bandwidth of 140 THz (from 608 THz to 748 THz), which is still remained well in the oblique incident angles for the TE-polarization. Our results can be regarded as the groundwork for the near future applications such as photodetectors, energy converters and more.

Spectrum Absorbency of Metamaterial Perfect Absorber

A triple-band metamaterial perfect absorber was introduced. The single and simple structure based on gold-bar shaped was designed on the 0.018λ Taconic TLY-5. The gold-bar shaped was designed horizontal initially was then being rotated anti-clockwise from0oto 90oto analyze and understand the change of absorption graph. Dual-band perfect metamaterial absorber was achieved at 45o. The fundamental and third harmonic magnetic resonances caused the low and high frequency peaks, respectively. Then, the gold-bar shaped was slotted at both end to create triple-band metamaterial perfect absorber. The slotted gold-bar shaped was evaluated in three absorption peaks: 99.94%, 99.88% and 99.66% at 3.98 GHz, 4.81 GHz and 5.33 GHz, respectively. This, however, moved to the 3.96 GHz, 4.80 GHz and 5.33 GHz with absorbency 99.79%, 99.95% and 99.90% for the measured structure. Both simulated and measure results were achieved absorbency over 99%, which was almost perfect absorption (≈100%). These properties are expected to beused in real-world applications such as satellite and radar communications transmission, particularly in lowering radar cross-section for stealth applications.

Dynamically dual-tunable dual-band to four-band metamaterial absorbers based on bulk Dirac semimetal and vanadium dioxide.

In this work, we investigate dynamically dual-tunable dual-band, triple-band, and four-band metamaterial absorbers (MAs) based on a bulk Dirac semimetal (BDS) and vanadium dioxide (VO2). Due to the bright-bright mode coupling between BDS rods, the dual-band, triple-band, and four-band MAs can be realized when the VO2 is in a fully metallic state. The average absorptivity of the absorption peaks in the three MAs reaches 97%, 98.6%, and 96.4% respectively. The physical mechanism can be explained by the radiating two-oscillator model. The resonant frequencies and absorptance intensities at absorption peaks in each MA can be dynamically tuned by varying the BDS Fermi energy and the VO2 conductivity.

Ultranarrow dual-band metamaterial perfect absorber and its sensing application

In this paper, a dual-band metamaterial absorber (MMA) with wide-angle and high absorptivity is proposed. The MMA consists of two silver layers separated by a dielectric layer. Its top resonant element is constituted by two concentric ring resonators connected with four strips. Based on electromagnetic field simulation, the proposed MMA has two narrow absorption peaks with an absorption rate of 99.9% at 711 nm and 99.8% at 830 nm, and the corresponding line width of the two absorption peaks are only 9.7 and 9.8 nm. The dual-band MMA shows high absorptivity under wide incident angles. The simulated field pattern shows that dual-band perfect absorption is the combined result of the interaction of two concentric ring resonators and unit cell coupling. In addition, the hexapole plasmon mode can be observed at the outer ring at one absorption peak. The narrow plasmon resonance has a potential application in optical sensing, and can be used to measure the concentration of aqueous glucose with two frequency channels. The proposed MMA with high absorptivity is simple to manufacture, and has other potential applications, such as narrow-band filters, energy storage device, and so on.

A polarization-insensitive, wide-angle dual-band tunable graphene metamaterial perfect absorber with T-shaped strips and square ring

Metamaterial perfect absorbers play an essential role in many optoelectronic devices. In this paper, a dual-band tunable metamaterial perfect absorber based on graphene is proposed. The simulation results present that under normal incidence two absorption peaks of 99.9% and 99.9% occur at the frequencies 1.69 THz and 4.30 THz, respectively. Impedance matching theory is employed to elaborate this dual-band perfect absorption phenomenon. While at oblique incidence, the absorption of the absorber remains more than 90% over a wide incident angle from 0° to 75° for the transverse electric (TE) polarization and 60° for the transverse magnetic (TM) polarization separately. Furthermore, it is also independent to the polarization angles. In addition, the effects of different geometrical parameters and the chemical potential of graphene on the resonant frequencies are investigated in detail. The two peaks of the absorber can be dynamically tuned by the variation of the chemical potential of graphene. Due to its good performances, the designed metamaterial perfect system has great potential applications in biosensing, photodetectors, stealth, and imaging devices.

Tunable dual-band metamaterial absorber in the infrared range based on split-ring-groove array.

In this paper, we present a tunable dual-band perfect metamaterial absorber working in the infrared band by integrating a metallic split-ring-groove resonator array with a liquid crystal (LC) layer atop a metal substrate. By varying the height of the central nanodisks, the absorptivity of the dual-band absorption peaks can be simultaneously adjusted. The dual-band resonance frequencies of the proposed absorber exhibit continuous tunability by adjusting the refractive index of the LC, which can be controlled by applying external voltage. The mechanism of the perfect absorption is attributed to the gap plasmonic resonance coupling regime. The presented absorber exhibits good tolerance to incidence angles up to 60° and shows polarization dependent performance, which may offer promising applications in sensing, modulator, and optical absorption switching in the infrared regime.

Dual-Band, Polarization-Insensitive, Ultrathin and Flexible Metamaterial Absorber Based on High-Order Magnetic Resonance

We demonstrate a dual-band, polarization-insensitive, ultrathin and flexible metamaterial absorber (MA), based on high-order magnetic resonance. By exploiting a flexible polyimide substrate, the thickness of MA came to be 1/148 of the working wavelength. The absorption performance of the proposed structure was investigated for both planar and bending models. In the case of the planar model, a single peak was achieved at a frequency of 4.3 GHz, with an absorption of 98%. Furthermore, additional high-order absorption peaks were obtained by the bending structure on a cylindrical surface, while the fundamental peak with a high absorption was maintained well. Our work might be useful for the realization and the development of future devices, such as emitters, detectors, sensors, and energy converters.

Dual-band metamaterial absorber with stable absorption performance based on fractal structure

In this paper, two kinds of dual-band metamaterial absorbers (MMAs) with stable absorption performance based on fractal structures are proposed. As the key feature, with the increase in fractal order, the fractal MMAs can reduce the weight while keeping the absorption performance. The multi-band absorption property is analyzed by multiple L-C resonances generated by the fractal structure. By virtue of good impedance matching characteristics and the synergy of the circuit and electromagnetic resonance, effective and stable microwave absorption is readily achieved. Finally, two prototypes are fabricated for demonstration, and the measurement result is consistent well with the simulation one. As expected, the proposed fractal MMAs have the advantage of low-cost, light-weight, and dual-effective absorption bands, and have great potential in the application of multi-band radar stealth.

Dual-band metamaterial absorber with a low-coherence composite cross structure in mid-wave and long-wave infrared bands.

The atmospheric window in the infrared (IR) band primarily consists of mid-wave (MWIR, 3-5 μm) and long-wave IR (LWIR, 8-12 μm) bands, also known as the working bands in most of the IR devices. The main factor affecting the device capability includes the absorption efficiency, hence, the absorption material. Herein, a dual-band absorber based on the composite cross structure (CCS) in both MWIR and LWIR bands was proposed, with absorption peaks of 4.28 μm and 8.23 μm. The obtained absorber is with high scalability in the MWIR and LWIR region respectively by tuning the structural parameters. A quadrupole polarization model is proposed for further understanding of the uneven distribution of electromagnetic field that was caused by the change of the center spacing of the embedded structure. Meanwhile, it was shown that the two absorption peaks exhibited good incident angle stability. In addition, as the incident angle of the TM mode increases, a waveguide is formed between the embedded structure and the surface structure, leading to another strong absorption in the LWIR band. The results showed that absorption increases as the incident angle increases. The proposed absorber can be a good candidate for applications in thermal emission, detection and solar energy harvesting.

Polarization insensitivity characterization of dual-band perfect metamaterial absorber for K band sensing applications

Polarization insensitive metamaterial absorbers (MA) are currently very attractive due to their unique absorption properties at different polarization angles. As a result, this type of absorber is widely used in sensing, imaging, energy harvesting, etc. This paper presents the design and characterization of a dual-band polarization-insensitive metamaterial absorber (MA) for K-band applications. The metamaterial absorber consists of two modified split ring resonators with an inner cross conductor to achieve a 90% absorption bandwidth of 400 MHz (21.4–21.8 GHz) and 760 MHz (23.84–24.24 GHz) at transverse electromagnetic (TEM), transverse electric (TE), and transverse magnetic (TM) mode. Polarization insensitivity of different incident angles for TE and TM mode is also investigated, which reveals a similar absorption behavior up to 90°. The metamaterial structure generates single negative (SNG) property at a lower frequency of 21.6 GHz and double negative property (DNG) at an upper frequency of 24.04 GHz. The permittivity and pressure sensor application are investigated for the proposed absorber, which shows its useability in these applications. Finally, a comparison with recent works is also performed to demonstrate the feasibility of the proposed structure for K band application, like sensor, filter, invasive clock, etc.

Design and Analysis of an Ultra-thin Dual-band Metamaterial Absorber for S-Band and X-Band

Design and Analysis of an Ultra-thin Dual-band Metamaterial Absorber for S-Band and X-Band

Polarization-insensitive dual-band terahertz metamaterial absorber based on asymmetric arrangement of two rectangular-shaped resonators

We present a design of a polarization-insensitive dual-band metamaterial absorber (MA) in the THz region by employing a three-layer structure consisting of a rectangular-shaped resonator on top of silicon and metallic film. Finite-difference time domain (FDTD) simulation indicates that two perfect absorption peaks can be achieved at 5.35 and 9.0 THz with absorptivity greater than 96% under normal incidence. The asymmetry in design structure eliminates any polarization dependence, and absorptivity is nearly 80% for large incidence angle up to 60°. The individual absorption band can be tuned by varying the dimensions of the rectangular-shaped resonator. The design idea provides a new strategy to achieve polarization-insensitive MA by arranging structure and can be extended to other bands.

Tunable dual-band metamaterial absorber at deep-subwavelength scale

A tunable dual-band metamaterial absorber composed of a gold square ring and a metal film separated by a strontium titanate dielectric is investigated. Two resonance peaks at frequencies 0.162 THz and 0.329 THz with over 99% absorbance are realized at room temperature. The maximum ratio between the lattice constant and the resonance wavelength is approximately 8.2%, which is much smaller than that of the formerly reported absorber. When the temperature changes from 150 K to 350 K, the two resonance absorption peaks at approximately 66.2% and 67.8% of the modulation depths are obtained. The effective impedance method and the LC equivalent circuit modelling are used to analyze the absorption mechanism of the proposed absorber. The proposed absorber is not affected by the change in polarization angles at normal incidence. The proposed structure adopts a single patterned square ring, which can be manufactured easily, and extended to other frequencies in applications such as biosensors, monitoring and imaging.

A Tunable “Ancient Coin”-Type Perfect Absorber with High Refractive Index Sensitivity and Good Angular Polarization Tolerance

In this paper, we design and present a graphene-based “ancient coin”-type dual-band perfect metamaterial absorber, which is composed of a silver layer, silicon dioxide layer, and a top “ancient coin” graphene layer. The absorption performance of the absorber is affected by the hollowed-out square in the center of the graphene layer and geometric parameters of the remaining nano disk. The optical properties of graphene can be changed by adjusting the voltage, to control the absorption performance of the absorber dynamically. In addition, the centrally symmetric pattern structure greatly eliminates the polarization angle dependence of our proposed absorber, and it exhibits good angular polarization tolerance. Furthermore, the proposed “ancient coin”-type absorber shows great application potential as a sensor or detector in biopharmaceutical, optical imaging, and other fields due to its strong tunability and high refractive index sensitivity.