Multi-band Metamaterial Absorber Research Articles

High sensitivity and high figure of merit graphene mid-infrared multi-band tunable metamaterial perfect absorber

In the research of this paper, we have devised a mid-infrared band metamaterial perfect absorber made of graphene material. The absorber is composed of a traditional three-layer structure of MPA. The top layer is a graphene layer with a specific structure, with SiO2 as the dielectric layer and the gold film as the substrate. In the wavelength range of 5500 – 13000 nm, the graphene layer generates seven absorption peaks and shows ultra-high absorption efficiency. The respective absorption rates are 91.17%, 99.41%, 99.01%, 95.69%, 94.16%, 96.89%, and 95.01%. By verifying the absorption spectra and the principle of effective impedance matching, analyze the electric field distribution image of the xoy plane based on the principle of surface plasmon resonance, we have proved that it conforms to the classical physical theory and expounded the reason why the absorption peaks were formed. The comparison of different graphene patterns has confirmed the superiority of this structure. By changing the relaxation time and Fermi level of graphene, the tunability of the absorber structure has been verified. Changing the incident angle has proved its insensitivity to the polarization angle (0° - 50°). Finally, by calculating and comparing the figure of merit (FOM) and the sensitivity (S), it is shown that this structure has significant sensitivity and excellent application ability and value. We firmly believe that our absorber can be well applied in high-sensitivity sensors, filters and detectors, and can contribute to fields such as photoelectric detection, optical communication and photoelectric sensing.

Robust Multi-Band DNG metamaterial absorber for GPS (L1), ISM, and 5G application with Enhanced polarization and angle stability

This research introduces a triple-band metamaterial absorber characterized by insensitivity to both polarization and incident angles. The structure includes square ring resonators on the upper side and a continuous metal ground on the lower side, separated by an FR4 substrate. At the lowest operating frequency, the unit cell’s thickness, and length measure 0.0128λ and 0.156λ, respectively. Under normal incidence, the proposed absorber demonstrates three clear absorption peaks at 1.56, 2.43, and 3.36 GHz, achieving absorption rates of 98 %, 99 %, and 97 %, respectively. The absorption response exhibits variation with incident angles up to 70° for both TM and TE polarizations due to its high-level symmetry. This configuration attains negative permittivity and permeability suitable for operational frequencies in the L-band and S-band. The study examines the electric field, impedance, and surface current to provide additional evidence for the absorption analysis. A validated RLC circuit equivalent to the proposed structure has been confirmed using Advanced Design System (ADS). The results indicate a slight deviation, especially at frequencies beyond the resonance frequencies. The structure underwent fabrication and testing in an anechoic chamber, revealing a strong correlation between the simulated and measured results. The suggested absorber holds promise for ISM applications, radar systems, sensing technologies, and energy harvesting systems.

Electric-Controlled Switching ON/OFF of Bands in a Graphene-Based Multi-band Metamaterial Absorber

Electric-Controlled Switching ON/OFF of Bands in a Graphene-Based Multi-band Metamaterial Absorber

Design and theoretical analysis of near-infrared multiband metamaterial absorber with concentric sub-resonators for solar applications

Metamaterial absorbers with multiple frequency bands can be designed by stacking sub-resonators vertically or arranging them co-planarly. However, to increase the number of absorption peaks, we often need more sub-resonators. Therefore, a study explores dynamic infrared multiband metamaterial absorbers to enhance electromagnetic wave absorption and addresses tunability challenges by utilizing a periodic sub-wavelength structure-based unit cell. The novel design comprises a concentric triangular strip within a central hollow of a square patch, with four hollow cylindrical spaces at the patch corners, each containing four small square pillars. The design comprises a metal–dielectric–metal architecture, with silver as the top patch and the ground metal layer separated by a thin magnesium fluoride dielectric layer. A temperature-controlled material vanadium dioxide layer is introduced below the upper metal layer to enhance the absorbance. Moreover, extensive parametric investigations have been conducted involving the manipulation of shape while keeping other dimensions constant. The goal is achieving perfect multiple absorptions within the 90–300 THz frequency range, ensuring impedance match and exhibiting plasmonic resonance characteristics. The study also investigates unit cell behavior regarding polarization and incident angle variations. Simulations are conducted using CST Microwave Studio Suite® with finite integration technology and validated with COMSOL Multiphysics® using the finite element method in the frequency domain. The simulated results reveal multiple absorption peaks in the terahertz range, averaging 98.32% with a maximum absorption of up to 99.99% and exhibiting high absorption coefficients at discrete resonance frequencies, suggesting promising applications in terahertz technology-related fields.

Theoretical investigation of enhanced terahertz metamaterial absorber integrated with blocked-impurity-band detector

Blocked-impurity-band (BIB) device becomes a prevalent terahertz detection technology, but its overall optical performance, such as quantum efficiency, is constrained by the thickness of the absorption layer. Metamaterial absorbers can effectively concentrate and absorb terahertz waves at a subwavelength scale, and their ultra-thin thickness facilitates device integration. A multi-band metamaterial absorber is developed and simulated tailored for the working band of Ge-doped BIB detectors. The design is founded on a three-layer structure with Ti rectangular resonator, Ge dielectric layer, and Ti reflective layer. This configuration achieves two absorption peaks at 74.16 μm and 92.09 μm, with optical absorption reaching 95.66% and 97.29%, respectively. The operating wavelength can be regulated by altering the geometric parameters of the rectangular resonator, and it exhibits angle-insensitive properties under small-angle incidence. These findings enhance the application of BIB detectors in terahertz detection technology, potentially improving their performance in deep space exploration.

Tunable multiband metamaterial perfect absorber based on a metal-graphene multilayer structure

Tunable multiband metamaterial perfect absorber based on a metal-graphene multilayer structure

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

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

Multiband highly sensitive metamaterial-based THz absorber for edible oil adulteration sensing

A terahertz (THz) wave technology is very appealing for applications in detection in biomedicine, biological spectroscopy, material characterization, detection, imaging, sensing, and other convenient applications. Metamaterials (MMs) are artificial structures that have structures in a regular periodic arrangement and don’t exist in nature. By utilizing a proposed terahertz metamaterial absorber, a broad spectrum of adulterated lubricants can be detected. It is an efficient detection process that enables the development of a THz detection approach by making use of the metamaterial as a sensor. The proposed terahertz absorber is analyzed and optimized using the CST Microwave Studio 2019 software. The article proposed a multiband THz metamaterial absorber with a unit size of 70 µm. According to the demonstrated results, we can achieve five narrow absorption peaks with perfect absorption within the frequency range between (0.2–4.2) Terahertz. Also, the result shows that, the average absorbance of 99.07% at the resonance frequencies of 0.56, 1.42, 2.676, 3.14, and 3.89 THz. The E (electric) and H (magnetic)-field distributions on the resonator at different resonance frequencies were also analyzed as well as. The recommended metamaterial absorber has a good sensing capability at different resonant frequencies, with refractive index sensitivities of 80 GHz/RIU, 240 GHz/RIU, 480 GHz/RIU, 480 GHz/RIU, and 520 GHz/RIU obtained by modifying the refractive index of the sample holder or the analytic layer, respectively. As a result, the proposed detector has a high refractive index sensitivity, high Q-factor, and high FOM, making it suitable for detecting oil adulteration.

A Polarization-Insensitive, Vanadium Dioxide-Based Dynamically Tunable Multiband Terahertz Metamaterial Absorber.

A tunable multiband terahertz metamaterial absorber, based on vanadium dioxide (VO2), is demonstrated. The absorber comprises a three-layer metal-insulator-metal (MIM) configuration with a split ring and slots of VO2 on the uppermost layer, a middle dielectric substrate based on silicon dioxide (SiO2), and a gold reflector on the back. The simulation results indicate that, when VO2 is in the metallic state, the proposed metamaterial exhibits nearly perfect absorption at six distinct frequencies. The design achieves an average absorption of 98.2%. The absorptivity of the metamaterial can be dynamically tuned from 4% to 100% by varying the temperature-controlled conductivity of VO2. The proposed metamaterial absorber exhibits the advantages of polarization insensitivity and maintains its absorption over 80% under different incident angle conditions. The underlying physical mechanism of absorption is explained through impedance matching theory, interference theory, and the distribution of electric fields. The ability to achieve multiband absorption with tunable characteristics makes the proposed absorber a promising candidate for applications in terahertz sensing, imaging, communication, and detection. The polarization insensitivity further enhances its practicality in various scenarios, allowing for versatile and reliable performance in terahertz systems.

Polarization insensitive multiband metamaterial absorber for bio-plastic sensing application

This article introduces a microwave multiband metamaterial absorber (MA) with high potential for bio-plastic sensing applications. The innovative design is realized through a compact unit cell dimension of 1.33λο × 1.33λο × 0.22λο, employing a state-of-the-art split-ring resonator structure. Strikingly, this absorber demonstrates polarization insensitivity and can be characterized by five distinct absorption peaks at 18.69 GHz, 23.34 GHz, 25.72 GHz, 32.94 GHz, and 35.40 GHz. The corresponding absorption rates are exceptionally high, ranging from 92.82% to 99.95%. To elucidate the underlying absorption mechanism, detailed analyses of the electric field, magnetic field, surface current distribution, and input impedance are provided, showcasing the absorber's effective MA structure. The designed MA sensor exhibits outstanding performance metrics for bio-plastic detection, including an average quality factor (Q-factor) of 210 and sensitivity of 0.888 GHz/RIU (refractive index unit), marking a significant advancement in the field. Additionally, the sensor's linearity, output variation, and sensitivity are considerably improved for bio-plastic sensing. The research confirms the proposed MA absorber's functionality by comparing measured results and simulation outcomes, indicating a high degree of accuracy and reliability. The potential applications of this MA are manifold, extending to microwave absorption and enhanced plastic sensing techniques. Its compact and thin design facilitates seamless integration with various sensor equipment, broadening the scope of its utility. Furthermore, the article delves into the relevance of this research to several Sustainable Development Goals (SDGs), particularly highlighting its alignment with SDG 9 (Industry, Innovation, and Infrastructure), SDG 12 (Responsible Consumption and Production), and SDG 14 (Life Below Water). Thus, the innovative MA design signifies a technological leap in the field of metamaterial absorbers and contributes to the pursuit of sustainability and environmental protection.

Polarization-independent and all-optically modulated multiband metamaterial coherent perfect absorber

A polarization-independent, all-optically modulated multiband metamaterial coherent perfect absorber (CPA) is proposed. Numerical simulation results reveal that the absorber can be controlled over a wide range of amplitudes by changing the phase difference of two incident light beams. The all-optical modulation can be extended to telecom wavelengths, allowing for simultaneous modulation of absorption at 1310 nm and 1550 nm. In addition, switchable logical gate states can be achieved at the dip between absorption peaks. The proposed absorber utilizes bound states in the continuum (BIC) mode to realize another absorption band, expanding the application range and enhancing its flexibility. The results suggest that the proposed absorber has a promising modulated optical response, with potential applications in developing optical switches, smart multi-band absorbers, telecom devices and so on.

Tunable, polarization-dependent multi-band perfect metamaterial absorber based on single layer mickey-like patterned graphene

This paper proposes and investigates a polarization-dependent multi-band perfect absorber composed of mickey-like patterned graphene. Simulation results demonstrate three perfect absorption peaks at 24.62 μm, 31.16 μm, and 65.12 μm with maximal absorbance of 96.6%, 98.8%, and 99.1% respectively, for instance, when an incident y-polarized wave is taken. A hybrid combination of the two ear and face structures effectively enhances and improves the absorption performance. This is evidenced by a step-by-step spectrum analysis of each decomposed and synthesized component, as well as an analysis of electric field coupling and impedance matching theory. Further investigation of the device's performance reveals that it is largely insensitive to incident angles (up to 30°), but is significantly affected by polarization angles due to the characteristic asymmetric properties of the structure along the x axis. The absorption peaks can be dynamically tuned by adjusting the effective parameters of graphene, the permittivity of the dielectric material, and the refractive index of its surroundings. Based on polarization related modulation mechanism, such graphene surface plasmon resonance (GSPR) induced device has potential applications in polarized light filtering, differentiation of dielectric materials, and sensing of surrounding refractive indices.

Multiband Metamaterial absorber with absorption prediction by assisted machine learning

This article presents a machine learning-based multiband metamaterial absorber (MMA) for terahertz applications that considerably reduces simulation time while ensuring accuracy. The designed MMA has absorption peaks at 2.93, 3.34, 3.88, 4.30, and 5.43 THz with absorption coefficients of 99.35, 87.12, 99.70, 99.70, and 99.71%, respectively. The proposed ultrathin and compact structure has a thickness of 0.031 λ and a periodic dimension of 0.199 λ corresponding to the lowest absorption frequency. Furthermore, the effect of changing the geometrical features of the MMA is investigated to realize the absorption phenomenon. The absorption coefficients at intermediate frequencies with substrate thickness, periodic dimension, and angles are predicted using extreme randomized tree (ERT) model. Regression models are assessed using an adjusted R2 score as an evaluation metric utilizing various values of nmin and test cases; TC-30, TC-40, and TC-50. The adjusted R2 score approaches 1 for a lower value of nmin, indicating that absorption values can be predicted with a high degree of accuracy. The regression analysis results suggest that the resource requirements can be reduced by 70% using the proposed ERT-based absorber model. The proposed highly efficient multi-band MMA design with machine learning behavior prediction capability can be used for sensing applications.

Optimization and modulation of a multiband multimode metamaterial absorber and its application in healthy hotel indoor gas sensing

Here, a multiple modes metamaterial absorber with four peaks was proposed and verified. All absorption peaks were excited by the multiple modes coupling between adjacent unit cells. By increasing the structural parameter D, absorption peaks were strengthened and shifteded to the low-frequency region. When the lattice constant P was increased, these peaks were decreased and shifteded to the high-frequency region. Similarly, when the dielectric layer thickness t 3 was gradually increased, these absorption peaks were weakened. Temperature was gradually increased, these absorption peaks were gradually reduced and shifteded to the high-frequency region. The multi-mode coupling effetct between unit cells was important to the performance of the metamaterial absorber.

Triple-Band Surface Plasmon Resonance Metamaterial Absorber Based on Open-Ended Prohibited Sign Type Monolayer Graphene.

This paper introduces a novel metamaterial absorber based on surface plasmon resonance (SPR). The absorber is capable of triple-mode perfect absorption, polarization independence, incident angle insensitivity, tunability, high sensitivity, and a high figure of merit (FOM). The structure of the absorber consists of a sandwiched stack: a top layer of single-layer graphene array with an open-ended prohibited sign type (OPST) pattern, a middle layer of thicker SiO2, and a bottom layer of the gold metal mirror (Au). The simulation of COMSOL software suggests it achieves perfect absorption at frequencies of fI = 4.04 THz, fII = 6.76 THz, and fIII = 9.40 THz, with absorption peaks of 99.404%, 99.353%, and 99.146%, respectively. These three resonant frequencies and corresponding absorption rates can be regulated by controlling the patterned graphene's geometric parameters or just adjusting the Fermi level (EF). Additionally, when the incident angle changes between 0~50°, the absorption peaks still reach 99% regardless of the kind of polarization. Finally, to test its refractive index sensing performance, this paper calculates the results of the structure under different environments which demonstrate maximum sensitivities in three modes: SI = 0.875 THz/RIU, SII = 1.250 THz/RIU, and SIII = 2.000 THz/RIU. The FOM can reach FOMI = 3.74 RIU-1, FOMII = 6.08 RIU-1, and FOMIII = 9.58 RIU-1. In conclusion, we provide a new approach for designing a tunable multi-band SPR metamaterial absorber with potential applications in photodetectors, active optoelectronic devices, and chemical sensors.

Penrose tiling-inspired graphene-covered multiband terahertz metamaterial absorbers.

In this work, we propose two different graphene-covered nanostructured metamaterial absorbers inspired by Penrose tiling. These absorbers allow spectrally tunable absorption within the terahertz spectrum corresponding to 0.2-20 THz. We have conducted finite-difference time-domain analyses to determine the tunability of these metamaterial absorbers. The proposed structures, Penrose models 1 and 2, perform differently from each other due to their design characteristics. Penrose model 2 reaches a perfect absorption at 8.58 THz. In addition, the relative absorption bandwidth calculated at full-wave at half-maximum in Penrose model 2 varies between 5.2% and 9.4%, which characterizes the metamaterial absorber as a wideband absorber. Also, we can observe that as we increase the Fermi level of graphene from 0.1 to 1 eV, the absorption bandwidth and relative absorption bandwidth both increase. Our findings show the high tunability of both models through varying graphene's Fermi level, the graphene's thickness, the substrate's refractive index, and the proposed structures' polarization. We can further observe multiple tunable absorption profiles that may find applications in designer infrared absorbers, optoelectronic devices, and THz sensors.

Constrained multi-objective optimization problem model to design multi-band terahertz metamaterial absorbers

The multi-band metamaterial absorbers studied today offer optimal sensing performance by maximizing the absorption at resonance frequencies. A constrained multi-objective optimization problem (CMOP) model is proposed to intelligently obtain the optimized geometrical parameters of the designed MA for optimal multi-band absorption. The proposed multi-band terahertz metamaterial absorber is formed by a patterned metallic patches (symmetric snowflake-shaped resonators) layer and a continuous metallic layer separated by a dielectric layer. The simulation results show that there are three discrete narrow resonance peaks with the absorption of 99.1%, 90.0%, and 99.9% in the range of 0.5–2 THz after being optimized by the proposed CMOP model. The reflection loss of all resonance modes is improved significantly compared with the conventional brute-force approach. Specifically, reflection loss at the highest resonance frequency is suppressed from -6.76 dB to -28.17 dB. Consequently, the reported MA design can be used as a refractive index sensor with the highest sensitivity of 495 GHz/RIU and the figure of merit (FoM) of 8.9 RIU−1 through a refractive index ranging from 1.0 to 1.6 at the analyte thickness of 18.5 μm. It is worth noting that most of the liquid samples have a refractive index ranging from 1.0 to 1.6. Therefore, the reported sensor can be used for liquid detection with high sensitivity.

Dual-band terahertz absorber based on square ring metamaterial structure.

In this paper, a dual-band terahertz absorber based on metamaterial structure is designed, fabricated, and measured. The metal periodic array is located on the upper surface of a silicon wafer with a metal ground plane, while the metamaterial structure is created utilizing a square metal ring with four T-shaped metal strips loaded inside of the ring. Two absorption peaks are realized at 0.715 and 1.013 THz with high Q-factors of 152.1 and 98.3, respectively, under normal TE and TM polarized incidence. A prototype of the proposed metamaterial absorber is fabricated by electron beam lithography (EBL) and electron beam evaporation (EBE) technology. Furthermore, a terahertz time-domain spectroscopy (TDS) measurement system is employed to test the absorber sample, with good measurement results obtained. This work provides a new option for the design of multi-band terahertz metamaterial absorbers.

Measurement and verification of a multi-band terahertz metamaterial absorber based on multiple coupling effects

Measurement and verification of a multi-band terahertz metamaterial absorber based on multiple coupling effects

Multiband polarization-insensitive cartwheel metamaterial absorber

Metamaterials are specifically engineered to produce electromagnetic properties that are not available in natural materials. Multiband metamaterial (MM) absorbers achieve great research interest due to their applications in sensing, filtering, and stealth. These absorbers are mostly made of multilayered and complex geometrical structures. In this work, a single-layered cartwheel-shaped (CWS), polarization-insensitive MM absorber operating in the microwave band is proposed. The absorber is discovered at four main resonance peaks at 13.64, 17.15, 18.4, and 19.23 GHz with an absorptivity above 0.9. It shows good angular stability, and multiple absorption peaks are attained due to multiple electric and magnetic resonances. Its characteristic has not been changed under different polarizations of incidence wave studied as 0°, 15°, 30°, 45°, 60° and 75°. When the absorber is examined with respect to the obliquity of the incidence wave in both TE and TM modes, the prominent absorption peaks exhibit an absorption performance above a ratio of 80%. Moreover, absorption characteristics can be tuned by modifying the substrate thickness. The comparison of simulated results and measured results shows good agreement with each other. This absorber would be useful for sensing and filtering applications in microwave devices.