Showing papers on "Metamaterial absorber published in 2021"
TL;DR: In this paper, a hybrid metamaterial absorber comprising a conventional magnetic absorbing material and a multi-layered meta-structure predesigned with graphene films is proposed to realize wideband absorption performance starting from ultra-low frequencies (0.79-20.9 GHz and 25.1-40.0 GHz).
Abstract: Developing high-efficiency microwave absorbers remains challenging in the broadband range, particularly in the low-frequency range containing the L band and even lower. To overcome this challenge, a hybrid metamaterial absorber comprising a conventional magnetic absorbing material and a multi-layered meta-structure predesigned with graphene films is proposed to realize wideband absorption performance starting from ultra-low frequencies (0.79-20.9 GHz and 25.1-40.0 GHz). The high absorption ability of the proposed device originates from fundamental resonance modes and their coupling. The experimental results agree well with the simulated ones, proving the effectiveness of our design method. In addition, owing to the use of low-density polymethylacrylimide foam and graphene films with outstanding mechanical properties, our design is lightweight and environmentally adaptable, which reflects its engineering value.
100 citations
TL;DR: In this article, a dual-frequency tunable ideal visible light metamaterial absorber based on the sub-wavelength range was proposed, which achieved perfect absorption in the visible light band.
Abstract: This paper proposes a dual-frequency tunable ideal visible light metamaterial absorber based on the sub-wavelength range, which achieves perfect absorption in the visible light band. The absorber consists of an Au reflector and a nodal (SiO2) layer, and a top Au absorber layer. The absorption structure on the top of the absorber adopts the style of ancient Chinese coins and forms a square arrays structure. As a result, the absorber's two absorption peaks are perfect absorption peaks, and the absorption rate can reach 99.9%. In addition, we also researched the influence of adjusting the absorber's geometric parameters on the absorber, and analyzed the absorption mechanism under different circumstances. Through research, it can be known that the absorber has near-perfect dual-band absorption characteristics that do not depend on polarization angle and incident angle insensitivity. Therefore, the absorber designed by us will have a broad application prospect in the filter, solar cell, and so on.
79 citations
TL;DR: In this paper, a terahertz bifunctional absorber with switchable functionalities of broadband absorption and multiband absorption was proposed, which obtains a broadband absorption with absorptance >90% from 3.25 THz to 7.08 THz.
Abstract: Based on the phase-transition property of vanadium dioxide (VO2), a terahertz bifunctional absorber is proposed with switchable functionalities of broadband absorption and multiband absorption. When VO2 is metal, the system is regarded as a broadband absorber, which is composed of VO2 patch, topas spacer, and VO2 film with metallic disks inserted. The system obtains a broadband absorption with absorptance >90% from 3.25 THz to 7.08 THz. Moreover, the designed broadband absorber has a stable performance within the incident angle range of 50°. When VO2 is dielectric, multiband absorption with six peaks is realized in the designed system. Graphene and the metallic disk-shaped array play the dominant role in the mechanism of multiband absorption. Through changing the Fermi energy level of graphene, the performance of multiband absorption can be dynamically adjusted. Because of the switchable functionalities, the proposed design may have potential application in the fields of intelligent absorption and terahertz switch.
71 citations
TL;DR: In this paper, a planar array with resistance-loaded metallic cross patterns and a vertical periodic crossed mesh array with resistive metallic ring patterns were used to improve the wide-angle polarization-independent absorption.
Abstract: In this article, by deliberately controlling multiple resistive electric and magnetic resonances in terms of dispersion and dissipation, a low-profile, wideband, microwave metamaterial absorber with wide-angle and polarization-independent responses is proposed. The proposed absorber comprises a planar array with resistance-loaded metallic cross patterns, and a vertical periodic crossed mesh array with resistance-loaded metallic ring patterns. The vertical periodic crossed mesh array was inserted between the planar array and the metal ground to improve the wide-angle polarization-independent absorption. The involved dispersion-engineered design strategy for angular- and polarization-insensitive responses is described with numerical evidences and electromagnetic response behaviors. A proof-of-concept absorber was fabricated and measured for verification. At quasi-normal incidence, the measured bandwidth characterized by more than 90% absorption was 2.11–3.89 GHz, i.e., a fractional bandwidth (FBW) of 59.3%. At the incident angle of 50°, the FBW of the absorption larger than 90% was 48.6%. The absorber was thin with a thickness of 13 mm, corresponding to $0.09\lambda _{0}$ at the lowest operating frequency. The numerical and experimental results demonstrated that our proposed strategy provides an effective way to achieve wide-angle and polarization-independent responses in a broadband; these responses are very promising for most strategic applications.
64 citations
TL;DR: In this article, a polarization-independent and angle-insensitive broadband THz graphene metamaterial absorber based on the surface plasmon-polaritons resonance was designed.
Abstract: In this paper, we design a polarization-independent and angle-insensitive broadband THz graphene metamaterial absorber based on the surface plasmon-polaritons resonance. Full-wave simulation is conducted, and the results show that the designed metamaterial absorber has an absorption above 99% in the frequency range from 1.23 THz to 1.68 THz, which refers to a very high standard. Furthermore, the absorber has the properties of tunability, and the absorption can be nearly adjusted from 1% to 99% by varying the Fermi energy level of the graphene from 0 eV to 0.7 eV. In the simulation, when the incident angles of TE and TM waves change from 0° to 60°, the average absorption keeps greater than 80%. The proposed absorber shows promising performance, which has potential applications in developing graphene-based terahertz energy harvesting and thermal emission.
60 citations
TL;DR: In this paper, a broadband metamaterial absorber with a fractional bandwidth of 126.88% was presented, and the characteristic mode theory was used to guide the design of the absorber.
Abstract: In this paper, a broadband metamaterial absorber with a fractional bandwidth of 126.88% was presented. The characteristic mode theory was used to guide the design of the absorber. According to the analysis of characteristic mode and characteristic current, the resistance value of resistive films can be determined. The different modal information obtained through parameter changes can also better guide the design of the absorber. To study its operation mechanism, the equivalent impedance and surface current distribution of the proposed absorber have been analyzed. The final simulation and measurement results show that the proposed absorber has a wide absorbing bandwidth which is from 3.21 to 14.35 GHz, and the absorptivity is greater than 90%, covering the S, C, X, and Ku bands. In addition, for TE and TM polarization, it can achieve an absorptivity of more than 85% at 45° oblique incident and has good angular stability. Hence, the absorber has great potential applications in the field of electromagnetic stealth technology and Radar Cross Section reduction.
43 citations
TL;DR: In this paper, a plasmon induced tunable metasurface based on multiband super-absorption in the infrared frequency regime is designed for sensing chemicals, monitoring the concentration of water-soluble glucose, and detecting viruses.
Abstract: An optically tunable perfect light absorber as a refractive index (RI) metamaterial (MM) nanobiosensor (NBS) is designed for sensing chemicals, monitoring the concentration of water-soluble glucose, and detecting viruses. This plasmon induced tunable metasurface works based on multiband super-absorption in the infrared frequency regime. It consists of a metal mirror that facilitates the MM to work as an absorber where the metal pattern at the top layer creates an enhanced evanescent wave that facilitates the metasurface to work as a RI optical sensor. The modelling and numerical analysis are carried out using Finite Difference Time Domain (FDTD) method-based software, CST microwave studio where a genetic algorithm (GA) is used to optimize the geometric parameters. We demonstrate multiband super-absorption spectra having maximum absorption of more than 99%. Furthermore, we show how the multiband super-absorber nanostructure can be used as a RI NBS, where the resonance frequency shifts with the RI of the surrounding medium. The achieved opto-chemical sensitivity is approximately ${65}{\textit {nm}}/{\textit {RIU}}~{\textit {RIU}}$ , the bio-optical sensitivity to detect viruses is approximately 76 nm $/$ RIU; and the optical sensitivity of the water-soluble glucose concentration is about ${300}{\textit {nm}}/ {\textit {RIU}}$ ; all sensitivities are comparable in comparison with the reported values in the literature.
42 citations
TL;DR: This study paves the way to the possibility of optical gas sensors and biosensors with high sensitivity with tunable split-disk metamaterial (SDM) absorbers.
Abstract: We present four designs of tunable split-disk metamaterial (SDM) absorbers. They consist of a bottom gold (Au) mirror layer anchored on Si substrate and a suspended-top SDM nanostructure with one, two, three, and four splits named SDM-1, SDM-2, SDM-3, and SDM-4, respectively. By tailoring the geometrical configurations, the four SDMs exhibit different tunable absorption resonances spanning from 1.5 µm to 5.0 µm wavelength range. The resonances of absorption spectra can be tuned in the range of 320 nm, and the absorption intensities become lower by increasing the gaps of the air insulator layer. To increase the sensitivity of the proposed devices, SDMs exhibit high sensitivities of 3312 nm/RIU (refractive index unit, RIU), 3362 nm/RIU, 3342 nm/RIU, and 3567 nm/RIU for SDM-1, SDM-2, SDM-3, and SDM-4, respectively. The highest correlation coefficient is 0.99999. This study paves the way to the possibility of optical gas sensors and biosensors with high sensitivity.
41 citations
TL;DR: In this paper, a specially designed metallic E-shaped fractal-based perfect metamaterial absorber (PMA) with fairly wideband absorptivity in the K- and Ka-bands of the microwave regime was investigated.
Abstract: A specially designed metallic E-shaped fractal-based perfect metamaterial absorber (PMA) with fairly wideband absorptivity in the K- and Ka-bands of the microwave regime was investigated. The PMA top surface is comprised of square-shaped split-ring resonators (SRRs) surrounded with the stated fractal design. The absorptivity of PMA was analyzed in the range of 20 – 30 GHz for the normal and oblique incidence of waves. Both the transverse electric (TE) and transverse magnetic (TM) modes were taken up to observe the robustness of the proposed design. It was observed that the fractal resonators exhibit capacitive effect at low frequencies, whereas the SRRs manifest capacitive effect at higher frequencies. The simulation and measured results were found to be in fairly good agreement. It is expected that the proposed design of PMA would be useful for 5G communication applications.
39 citations
TL;DR: In this paper, a thermally switchable terahertz metamaterial absorber consisting of an array of orthogonal coupled split-ring metal resonators involving a VO2 phase transition was designed and demonstrated.
Abstract: We design and demonstrate a thermally switchable terahertz metamaterial absorber consisting of an array of orthogonal coupled split-ring metal resonators involving a VO2 phase transition. Numerical results indicate that the active metamaterial always absorbs the TE wave in dual-band regardless of insulating and metallic VO2, while the insulator-to-metal phase transition enables a switchable effect between dual-band and broadband absorption of the TM wave with the resonant frequency tunability of 33%. Especially under the metallic VO2 state, the absorption properties are polarization-dependent and exhibit a switching effect between dual-band and broadband absorption with the increase of the polarization angle. The tunable absorption mechanism can be explained by effective impedance theory and electric energy density distributions. The proposed dual-band to broadband metamaterial switching absorber may have broad applications in sensors, imaging and emitters.
35 citations
TL;DR: In this article, a metamaterial absorber with hierarchical structures was designed and realized, which can display an averaged -19.4 dB reflection loss (∼99% absorption) from 3 to 40 GHz.
Abstract: By introducing metallic ring structural dipole resonances in the microwave regime, we have designed and realized a metamaterial absorber with hierarchical structures that can display an averaged -19.4 dB reflection loss (∼99% absorption) from 3 to 40 GHz. The measured performance is independent of the polarizations of the incident wave at normal incidence, while absorption at oblique incidence remains considerably effective up to 45°. We provide a conceptual basis for our absorber design based on the capacitive-coupled electrical dipole resonances in the lateral plane, coupled to the standing wave along the incident wave direction. To realize broadband impedance matching, resistive dissipation of the metallic ring is optimally tuned by using the approach of dispersion engineering. To further extend the absorption spectrum to an ultrabroadband range, we employ a double-layer self-similar structure in conjunction with the absorption of the diffracted waves at the higher end of the frequency spectrum. The overall thickness of the final sample is 14.2 mm, only 5% over the theoretical minimum thickness dictated by the causality limit.
TL;DR: In this article, a metamaterial absorber composed of a double-open rectangular ring and a graphene strip cross structure was proposed to achieve perfect absorption at 2.88 GHz (1.260-1.548 THz).
Abstract: The applications of terahertz waves and metamaterials in electromagnetic wave absorbers are one of the key focus areas of current interdisciplinary scientific research. In this study, we propose a metamaterial absorber composed of graphene double-open rectangular ring and graphene strip cross structures. The experiment uses numerical analysis software to study the proposed absorber. Transverse electric waves were normally incident on the absorber from the plane port, where resonance coupling was achieved. With an increase in the incidence angle alpha, the trough in the middle of the absorption spectrum continued to deepen. The bandwidth that the spectral absorption maintains above 0.9 is 2.88 GHz (1.260–1.548 THz). The maximum spectral absorption has reached 99.9%, which is approximately perfect absorption. The absorber under transverse magnetic wave incidence also exhibited a bandwidth advantage. As the Fermi energy continued to increase, the absorption bandwidth first increased and then decreased, and reached the maximum at ef = 0.5 eV. Simultaneously, the relative absorption bandwidth also reached its maximum. By adjusting the Fermi level of graphene, dynamic tuning of the metamaterial absorber could be achieved. Adjustment of the Fermi level shifted the absorption range and absorption bandwidth, and helped in controlling the increase in the relative absorption bandwidth. The findings of this study can be of theoretical and engineering significance in the domains of thermal photovoltaics, solar cells, and sensors, among others.
TL;DR: In this article, the authors reported a new design of a broadband absorber composed of graphene, dielectric, and gold layers, which can be used for applications in the far infrared frequency range due to choosing optimized dimensions and the graphene Fermi level.
Abstract: This paper reports a new design of a broadband absorber composed of graphene, dielectric, and gold layers. The designed absorber has four absorbent modes close to each other, which results in the formation of broadband absorption. The relative bandwidth, a key parameter to assess the bandwidth improvement, shows a significant increase in the proposed design compared to similar structures published in recent years. The numerical results also reveal this metamaterial absorber can be used for applications in the far-infrared frequency range due to choosing optimized dimensions and the graphene Fermi level. Unlike other graphene-based metamaterials, which require complicated structures to be able to attain broadband absorption, the physical structure of the proposed design has a relatively simple fabrication process. For further investigations, the effect of split geometry on the absorption spectrum is studied. Also, the use of graphene in this metamaterial absorber provides dynamic adjustability through electrostatic doping in order to tune the amount of absorption. This characteristic has been studied by changing the graphene Fermi level. This feature can be widely used in electro-absorption switches and modulators.
TL;DR: In this article, a dual-tunable broadband metamaterial absorber based on bulk Dirac semimetal (BDS) and water is proposed in the terahertz (THz) region.
Abstract: A dual-tunable broadband metamaterial absorber based on bulk Dirac semimetal (BDS) and water is proposed in the terahertz (THz) region. Different from the traditional single controlled absorber, this proposed absorber can be adjusted by temperature and Fermi energy level. Simulation results indicate that the absorptance greater than 90% is achieved in the frequency range of 3.05 to 6.35 THz under normal incidence, when the temperature of the water and Fermi energy level of BDS are adjusted at 15 ℃ and 30 meV, respectively. Compared with the absorber without injected water or no BDS pattern, the bandwidth with absorptance over 90% has been significantly improved. Moreover, absorption bandwidth and intensity can be controlled independently or jointly by adjusting the temperature of the water or the Fermi energy of BDS instead of redesigning the devices. The mechanism of the proposed dual-controlled absorber is explained by utilizing the permittivity of water can be adjusted by different temperatures, and BDS can be controlled by employing the Fermi energy. Field analysis is introduced to investigate and elucidate the physical origin of broadband absorption. Based on the remarkable performance, our results may have potential applications in the thermal detectors and terahertz imaging areas.
TL;DR: In this paper, a tunable and transparent metamaterial absorber with a water-based substrate is presented, with high optical transparency and broadband microwave absorptivity, covering an ultrawide frequency range of 5.8-16.2 GHz, while the average optical transmittance is ∼70.18%.
Abstract: A tunable and transparent metamaterial absorber (MMA) with a water-based substrate is presented, with high optical transparency and broadband microwave absorptivity. In the material structure, indium–tin–oxide (ITO) films are included as the resonant pattern and reflective layers, and distilled water is combined with polymethyl methacrylate (PMMA) to produce the dielectric substrate. By effectively designing its structural parameters, the proposed absorber achieves >90% absorptivity, covering an ultrawide frequency range of 5.8–16.2 GHz, while the average optical transmittance is ∼70.18% over a wavelength range of 400–800 nm. Moreover, owing to a specific design feature, the absorber has high polarization insensitivity and wide-incident-angle stability for transverse electric (TE) and transverse magnetic (TM) polarization waves. Furthermore, the absorption properties of the absorber can be further tuned by controlling the thickness of the water substrate. Both numerical simulations and experimental measurements demonstrate the excellent performance of the device, showing its strong potential for use in optical windows within military and medical equipment.
TL;DR: In this paper, an optimal metamaterial absorber with perfect spectrally selective performance was obtained after optimizing the structure of the four-pointed star prisms, achieving a high solar-to-heat efficiency of 92.31-77.78% at 1000 suns and 1273-1673 K.
TL;DR: In this article, a stereoscopic multilayered ultrabroadband metamaterial absorber by stacking multilayer concentric resonators on different-level top surfaces of a monolithic three-dimensional (3D) pagodalike substrate was proposed.
Abstract: Terahertz (THz) absorbers have recently attracted extensive attention for their promising potential in various applications; however, many existing THz absorbers are restrained by their narrow bandwidth and complicated and costly fabrication process that renders them unfavorable for practical devices. Herein, we propose a stereoscopic multilayered ultrabroadband THz metamaterial absorber by stacking multilayer concentric resonators on different-level top surfaces of a monolithic three-dimensional (3D) pagodalike substrate. By taking full advantage of the 3D printing technique, the proposed ultrabroadband absorber can be produced efficiently in an easy three-step process that overcomes the fabrication complexities of traditional multistep photolithography processes. Additionally, the feasibility and robustness of the proposed fabrication method for common out-of-plane THz narrowband absorbers are also validated, and the absorption capacities of the 3D printed absorbers are numerically and experimentally elucidated. These results might provide an efficient concept and fabrication technique to stimulate many potential applications in emerging THz technologies, such as sensing, imaging, and wireless communications.
TL;DR: In this article, a dual-band tunable absorber with a graphene-dielectric-metal structure was proposed as a sensor in the terahertz (THz) region.
TL;DR: In this paper, a dual-band polarization-insensitive metamaterial absorber (MA) for K-band applications is presented, which 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).
Abstract: 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.
TL;DR: This presented terahertz metamaterial absorber with a triple-band absorption and easy fabrication can find important applications in biological sensing, THz imaging, filter and optical communication.
Abstract: We presented and manufactured a triple-band terahertz (THz) metamaterial absorber with three concentric square ring metallic resonators, a polyethylene terephthalate (PET) layer, and a metallic substrate. The simulation results demonstrate that the absorptivity of 99.5%, 86.4%, and 98.4% can be achieved at resonant frequency of 0.337, 0.496, and 0.718 THz, respectively. The experimental results show three distinct absorption peaks at 0.366, 0.512, and 0.751 THz, which is mostly agreement with the simulation. We analyzed the absorption mechanism from the distribution of electric and magnetic fields. The sensitivity of the three peaks of this triple-band absorber to the surrounding is 72, 103.5, 139.5 GHz/RIU, respectively. In addition, the absorber is polarization insensitive because of the symmetric configuration. The absorber can simultaneously exhibit high absorption effect at incident angles up to 60° for transverse electric (TE) polarization and 70° for transverse magnetic (TM) polarization. This presented terahertz metamaterial absorber with a triple-band absorption and easy fabrication can find important applications in biological sensing, THz imaging, filter and optical communication.
TL;DR: In this paper, a metal-dielectric metamaterial absorber is proposed to achieve ultrabroadband absorption at frequencies from ultraviolet to near-infrared, based on finite element method solutions.
Abstract: In this paper, a metal-dielectric metamaterial absorber is proposed to achieve ultrabroadband absorption at frequencies from ultraviolet to near-infrared. Based on finite element method solutions, the average absorption of the absorber is 97.75% from 382 nm to 1100 nm, with a maximum of 99.92%, resulting from multiple resonance coupling. The influences of geometric parameters and incident conditions on absorption are investigated. Broadband and narrowband absorption changes are realized by changing incident light polarization. Polarization-independent properties can be realized by changing the dielectric structure to centrosymmetric. The average absorption of the polarization-independent structure is 97.11% from 250 nm to 1115 nm, with a maximum of 99.98%. The proposed absorber structure has wide optical applications including solar energy harvesting and light-emitting devices.
TL;DR: In this article, a tunable low-frequency acoustic absorber composed of multi-layered ring-shaped microslit tubes with a deep subwavelength thickness was proposed to fit the actual noise spectrum.
Abstract: Current sound-absorbing materials have fixed absorption spectra due to unalterable local resonance properties, which limit their application potential in many noise control scenarios. Clear motivation exists, therefore, to design an acoustic absorber to fit the actual noise spectrum with reconfigurable geometry and subwavelength thickness. Here, we analytically present and experimentally verify a tunable low-frequency acoustic absorber composed of multi-layered ring-shaped microslit tubes with a deep subwavelength thickness. This decreases the working frequency and significantly increases the acoustic absorption efficiency simultaneously. A physical model of the proposed metastructure is established on the basis of an acoustic equivalent circuit using microslit absorber theory. Superior impedance manipulation capability is achieved by rotating the middle microslit tube from 0° to 180°. This enables continuous tunability of the metamaterial absorber over a wide working frequency band. In both the simulated and measured results, highly efficient acoustic absorption (at least 0.9) is achieved in the range of 280–572 Hz. Simulations under oblique incidence are conducted to validate the wide-angle performance of the absorber. Based on the proposed tunable absorption mechanism, a hybrid metamaterial absorber is designed to produce adjustable broadband absorption with high efficiency. Our work helps pave the way to absorbing metamaterials being used in practical engineering applications such as noise control due to the advantages of tunable functionality, compactness, high efficiency, wide-angle absorption, and easy fabrication.
TL;DR: In this article, an optically transparent broadband metamaterial absorber (MA) containing an air layer and a water layer is proposed, which can absorb broadband microwave and reduce infrared radiation at the same time.
TL;DR: In this paper, a tunable broadband metamaterial absorber is proposed based on the vanadium dioxide and Fabry-Perot cavity in the terahertz region, which can be approximately tuned from 8% to 100% by changing the conductivity of vanadium oxide.
TL;DR: In this article, a terahertz (THz) metamaterial absorber made of stainless steel was presented, and the absorption rate reached 99.95% at 1.563 THz.
Abstract: This paper presents a terahertz (THz) metamaterial absorber made of stainless steel. We found that the absorption rate of electromagnetic waves reached 99.95% at 1.563 THz. Later, we analyzed the effect of structural parameter changes on absorption. Finally, we explored the application of the absorber in refractive index sensing. We numerically demonstrated that when the refractive index (n) is changing from 1 to 1.05, our absorber can yield a sensitivity of 74.18 μm/refractive index unit (RIU), and the quality factor (Q-factor) of this sensor is 36.35. Compared with metal–dielectric–metal sandwiched structure, the absorber designed in this paper is made of stainless steel materials with no sandwiched structure, which greatly simplifies the manufacturing process and reduces costs.
TL;DR: In this paper, a wideband and polarization-insensitive absorber based on graphene for terahertz (THz) applications is presented, where two concentric rectangular rings with cross-shaped strips are combined on a silicon substrate.
TL;DR: A multi-band, ultrathin, polarization-insensitive, near-perfect metamaterial absorber (PMA) has been proposed and substantiated numerically for solar thermophotovoltaic (STPV) systems which also can be used in some other applications as discussed by the authors.
Abstract: A multi-band, ultrathin, polarization-insensitive, near-perfect metamaterial absorber (PMA) has been proposed and substantiated numerically for solar thermophotovoltaic (STPV) systems which also can be used in some other applications. This kind of absorber currently drawing massive interest throughout the research of optics. Especially in solar harvesting metamaterial absorbers can give a huge boost in efficiency by intensifying the solar electromagnetic wave. Visible wavelength has been the key focus of the proposed design so that the structure can utilize solar energy proficiently. Aluminum (Al) and Gallium Arsenide (GaAs) have been chosen as materials for their higher electron mobility along with good temperature stability. The PMA is a three-layer metal-dielectric-metal called sandwiched structure. For proper characterization of the PMA absorber, extensive parametric inspections were carried out with underlying physics. The finite integration technique (FIT) in computer simulation technology microwave studio (CST MWS) is used to perform the numerical analysis and for verification finite element method (FEM) in COMSOL Multiphysics has been used along with interference theory model (ITM) for calculating the absorbance. The PMA shows 99.27%, 99.89%, 99.91%, and 99.06% perfect absorption at 454.75nm, 505.53nm, 568.72nm, and 600.85nm resonance wavelength in all three modes of waveguide propagation. The design also exhibits incident wave stability up to 60° for both transverse electric (TE), and transverse magnetic (TM) wave modes. Excellent glucose concentration sensing ability was also observed with the proposed structure. So, the proposed PMA can be implemented in solar energy harvesting devices along with solar sensors or detectors, light trappers, light modulators, or light wavelength detectors.
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TL;DR: In this article, a tungsten-polyurethane composite that is impedance-matching to water while simultaneously having a much slower longitudinal sound speed is proposed, and experimentally realized, an underwater acoustic absorber exhibiting high absorption from 4 to 20 kHz.
Abstract: By using a structured tungsten-polyurethane composite that is impedance-matched to water while simultaneously having a much slower longitudinal sound speed, we have theoretically designed, and experimentally realized, an underwater acoustic absorber exhibiting high absorption from 4 to 20 kHz, measured in a 5.6m times 3.6m water pool with the time-domain approach. The broadband functionality is achieved by optimally engineering the distribution of the Fabry-Perot resonances, based on an integration scheme, to attain impedance matching over a broad frequency range. The average thickness of the integrated absorber, 8.9 mm, is in the deep subwavelength regime (~{\lambda}/42 at 4 kHz) and close to the causal minimum thickness of 8.2 mm that is evaluated from the simulated absorption spectrum. The structured composite represents a new type of acoustic metamaterials that has high acoustic energy density and promises broad underwater applications.
TL;DR: In this paper, the authors reported an ultrabroadband perfect metamaterial absorber, comprising a two-dimensional array of a hemi-ellipsoid shaped metallo-dielectric multilayered structure.
Abstract: We report an ultrabroadband perfect metamaterial absorber, comprising a two-dimensional array of a hemi-ellipsoid shaped metallo-dielectric multilayered structure. What we believe, to the best of our knowledge, is an unprecedented average absorbance of ∼99% is theoretically demonstrated in the 300 to 4500 nm spectral range at normal incidence. We use 20 pairs of molybdenum–germanium metallo-dielectric layers with tungsten as the ground metal placed on a silicon substrate. Our design is polarization-independent as well as angle-insensitive (up to 60°), making it a perfect “superabsorber.” Theoretical modeling based on effective medium theory validates our full-wave simulation results. The figure-of-merit calculations suggest that our superabsorber can outperform recently reported broadband absorbers. The proposed design has potential application in thermophotovoltaics for solar energy harvesting.