Power Loss Density Distributions Research Articles

Research and simulation of electromagnetic wave absorbing performance for lightweight cement-based materials containing expanded polystyrene with different particle sizes and carbon black

The electromagnetic wave (EMW) absorbing performance of cement-based materials incorporating expanded polystyrene (EPS) with varying particle sizes is comprehensively studied through a combination of experimental and simulation methods. The addition of conductive carbon black (CB) to the cement matrix significantly increases the conductivity and dielectric constant, thereby improving the loss capacity. The frequency shift behavior of single and three-layer absorbing materials adheres to the effective medium theory and interference cancellation principle. The enhancement in overall EM parameters leads to a shift of the reflection loss (RL) peak towards lower frequencies. For three-layer materials, an increase in the thickness of absorbent layer proves beneficial for enhancing absorption performance. Simulations can effectively model cement-based materials by employing uniform material settings, with the size of EPS particles serving as the primary variable. The simulation results reveal that an increase in EPS particle size, in both single-layer and multi-layer materials, causes a shift of the RL peak towards lower frequencies. Additionally, analysis of electric field mode distribution and EM power loss density distribution indicates that scattering at the curved EPS interface alters the propagation direction of EMWs, increasing opportunities for loss inside the cement-based material. Moreover, the three-layer absorbing material, with a density ranging from 850 to 900 kg/m3 and compressive strength exceeding 4 MPa, is suitable for EMW absorption in building envelope structures. In conclusion, an increase in EPS particle size and CB content leads to a low-frequency shift of the RL absorption peak. This discovery not only provides an empirical foundation for the development of absorption materials tailored to specific frequency bands but also offers an efficient approach for repurposing waste EPS of diverse sizes. Furthermore, the grading of EPS with different particle sizes has important practical significance for increasing the content of EPS and preparing lightweight cement-based materials.

Ultrathin Narrowband and Bidirectional Perfect Metasurface Absorber

The conventional design approaches for achieving perfect absorption of electromagnetic (EM) waves using metasurface absorbers (MSAs) are limited to absorbing waves in one direction while reflecting waves in the other. In this study, a novel ultrathin narrowband MSA with bidirectional perfect absorption properties has been proposed, based on a tri-layer metal square-circular-square patch (SCSP) structure. The simulation results demonstrate that the proposed MSA exhibits a remarkable absorbance of 98.1%, which is consistent with the experimental and theoretical calculations. The equivalent constitutive parameters that were retrieved, as well as the simulated surface current and the power loss density distributions, reveal that the perfect absorption of the designed MSA originates from the fundamental dipolar resonance. Furthermore, the proposed MSA demonstrates stable wide-angle absorption properties for both transverse electric (TE) and transverse magnetic (TM) waves under various oblique incidence angles. The absorption characteristics of the MSA can be fine-tuned by adjusting the structural parameters. Additionally, the proposed MSA boasts excellent ultrathin thickness, bidirectional, polarization-insensitive, and wide-angle properties, making it highly suitable for a range of potential applications such as imaging, detection, and sensing.

Absorptive/transmissive frequency selective surface with multiple transmission zeros for reduced transition bandwidth

An absorptive/transmissive frequency selective surface (ATFSS) with multiple transmission zeros is proposed, which consists of one lossy layer and two lossless layers separated by air space. As the key features, the slot-line loading and interlayer coupling technologies are adopted in the lossy layer and lossless layers, respectively, to introduce the infinite impedance points and four transmission zeros, thereby simultaneously achieving low insertion loss and high selectivity of the transmission band. Benefiting from the ohmic loss of the lumped resistance in the lossy layer, effective absorption can be readily implemented. A detailed qualitative analysis of the proposed structure is presented through the equivalent circuit theory, surface current, and power loss density distributions. Under normal incidence, the overall structure exhibits two discrete absorption bands over the frequency range of 6.34 to 13.40 GHz, whereas a transmission behavior is obtained from 9.34 to 11.40 GHz with a minimum insertion loss of only 0.14 dB. In particular, there are only 3.9% and 3% transition bandwidths between absorption and transmission functions. Then, a sample prototype is fabricated for demonstration, and the measured results are well consistent with the simulated one. As expected, the proposed ATFSS has the advantage of multiple transmission zeros, loss insertion loss, and narrow transition band, which is of great potential in the application of radar stealth radome.

Microwave polarization conversion and reflection loss mechanism of complementary-modeled Rossler-based chaotic metamaterial

The complementary-modeled Rossler chaotic metamaterial (CRCM) with FR-4 dielectric layer is proposed to design metamaterial absorber with multi-resonance peaks. Under “master-slave” boundary condition in high-frequency structure simulator (HFSS) software, the electric field between adjacent boundaries presents phase difference which can simulate an infinite array. The research results show that the CRCM demonstrates multi-resonant peaks from 4 GHz to 10 GHz, and the area of metal patterned-layer can obviously regulate the resonant peaks. The CRCM presents a linear polarization conversion peak around 5.80 GHz, its polarization conversion ratio (PCR) is near 100%. The PCR is also larger than 80% from 5.56 GHz to 5.95 GHz. Through the surface current density distribution and the comparison between the CRCM and complementary-modeled double ring metamaterial (CDRM), the main factors generating polarization conversion are the asymmetry of metal pattern layer and magnetic resonance caused by reverse current. The CRCM also has two strong absorption peaks located at 6.31 and 9.37 GHz, respectively. Dielectric loss and ohmic loss are the main microwave loss mechanisms proved by volume and surface power loss density distribution. The resonant frequencies derived from [Formula: see text] resonant circuit are well consistent with the simulation data and measurement results.

3D metamaterial ultra-wideband absorber for curved surface

This paper proposes a three-dimensional metamaterial absorber based on a resistive film patch array to develop a low-cost, lightweight absorber for curved surfaces. An excellent absorption over a large frequency band is achieved through two different yet controllable mechanisms; in the first mechanism, a considerable attenuation in the wave power is achieved via graphite resistive films. The absorption is then intensified through magnetic dipoles created by the surface currents, leading to absorption peaks. The simulation results of the absorber show that a broadband absorption greater than 85% is achieved over 35–400 GHz for both TE and TM polarization waves at normal incidence. The structure has more than 167% and 80% absorption bandwidth above 85% and 90%, respectively. It is shown that the proposed metamaterial absorber is independent of incident wave polarization. In addition, the structure is insensitive to incident angles up to 60° for TE mode and full range angle 90° for TM mode. To describe the physical mechanism of the absorber, E-field, power loss density and surface current distributions on the structure are calculated and shown. Moreover, the oblique incidence absorption efficiency is also explained. This absorber paves the way for practical applications, such as sensing, imaging and stealth technology. In addition, the proposed structure can be extended to terahertz, infrared and optical regions.

Dual-band tunable terahertz perfect absorber based on all-dielectric InSb resonator structure for sensing application

A dual-band terahertz (THz) perfect absorber (PA) based on the all-dielectric metamaterial (MM) composed of the vertical-square-split-ring (VSSR) structure InSb array was proposed and investigated numerically. Simulation results show that the absorbance of the proposed PA under room temperature T = 295 K is up to 99.9% and 99.8% at 1.265 THz and 1.436 THz, respectively, which is consistent well with the fitting results of coupling mode theory (CMT). According to the simulated electric field and power loss density distributions, the perfect absorption results from the excitation of the first- and second-order plasmonic resonance mode. Further results show that the designed PA is polarization-insensitive due to the high geometric rotational symmetry, and wide-angle absorption can be achieved for transverse magnetic (TM) waves. The geometric parameters of the VSSR structure InSb and the external environment temperature can be changed to adjust the resonance absorption properties of the designed dual-band PA. The dual-band PA can be functioned as a temperature sensor with a sensitivity of about 5.9 GHz/K and 6.4 GHz/K, respectively. Furthermore, the dual-band PA under T = 295 K also can be served as a refractive index sensor with a sensitivity of about 1.3 THz/RIU and 1.0 THz/RIU, respectively. Due to its excellent properties including simple design, easy fabrication, polarization-insensitive and perfect absorption, the proposed dual-band PA may find many potential applications in detecting, imaging, and sensing in the THz region.

Single-layer absorption-diffusion-integrated metasurface for high-performance radar cross section reduction using hybrid copper–graphene structure

Numerous studies have been made to design absorption–diffusion–integrated metasurface (ADIM) for the application of electromagnetic stealth. However, it is still a challenge to achieve an outstanding stealth effect and a simple structure simultaneously. In this article, we propose two simple hybrid copper–graphene units with similar absorptivity and a reflected phase difference of pi, which are utilized to construct a novel ADIM by using a simulated annealing algorithm with a scattering pattern prediction module. A sample with an overall size of 200 × 200 mm2 is designed, fabricated, and measured. Both simulation and experimental results are in good agreement, which fully demonstrate the design method. The proposed ADIM with only a single functional layer exhibits more than 20 dB radar cross section reduction from 7.5 to 13.5 GHz maintained to 20° oblique incidence, which could address this challenge successfully. Power loss density and surface current distributions of the proposed two units are given to provide a physical insight of the mechanisms. The proposed ADIM can enable a wide application in stealth cloak, microwave imaging, wave front manipulation, and so on.

Computational Investigation of Multiband EMNZ Metamaterial Absorber for Terahertz Applications

This study presents an Epsilon Mu near-zero (EMNZ) nanostructured metamaterial absorber (NMMA) for visible regime applications. The resonator and dielectric layers are made of tungsten (W) and quartz (fused), where the working band is expanded by changing the resonator layer's design. Due to perfect impedance matching with plasmonic resonance characteristics, the proposed NMMA structure is achieved an excellent absorption of 99.99% at 571 THz, 99.50% at 488.26 THz, and 99.32% at 598 THz frequencies. The absorption mechanism is demonstrated by the theory of impedance, electric field, and power loss density distributions, respectively. The geometric parameters are explored and analyzed to show the structure's performance, and a near-field pattern is used to explain the absorption mechanism at the resonance frequency point. The numerical analysis method describes that the proposed structure exhibited more than 80% absorbability between 550 and 900 THz. The Computer Simulation Technology (CST Microwave Studio 2019) software is used to design the proposed structure. Furthermore, CST-HFSS interference is validated by the simulation data with the help of the finite element method (FEM). The proposed NMMA structure is also exhibits glucose concentration sensing capability as applications. So the proposed broadband absorber may have a potential application in THz sensing, imaging (MRI, thermal, color), solar energy harvesting, light modulators, and optoelectronic devices.

Broadband water-based metamaterial absorber for millimeter-wave, high-power applications

An all-dielectric metamaterial absorber based on water resonator encapsulated in resin container is proposed. The absorber can afford the maximum absorption up to 98% at 190 GHz, as well as the wide absorption frequency range from 115 GHz to 300 GHz and a nearly 90% relative absorption bandwidth. The role of water resonator sealed in the resin shell in improving absorption capability is demonstrated by the comparison result that the proposed absorber is superior to pure water or pure resin absorber with the same dimension and interpreted by a further study on the fields and power loss density distributions. Moreover, the proposed absorber can remain excellent absorption performance even for the oblique incidence with large angles. Besides the outstanding absorption performance, the proposed absorber has the advantage of low cost endowed by the use of water, which makes it promising for EM compatibility in the millimetre-wave and high-power cases.

3D rampart-based dual-band metamaterial absorber with wide-incident-angle stability

We propose a dual-band metamaterial absorber (MA) based on a stereo resonant structure. The unit cell of the proposed MA is composed of double metallic rings with a rampart on each ring into a dielectric substrate. In contrast to the conventional plane resonator, our proposed metamaterial exhibits wider incident angle stability. The power loss density distribution shows that the standing ramparts play a key role in enhancing the electromagnetic wave absorption. Experimental results verify the wide-incident-angle stability of the absorber. Our proposed strategy paves a new way on developing MAs with wide incident angle stabilities.

Plasmon nanoparticle effect to improve optical properties of perovskite thin film

Noble metal material, size, period and position are key parameters to affect optical absorption property of perovskite thin film, which was numerically investigated in this paper by finite element method. It demonstrates that Al nanoparticles show larger enhancement ability of light absorption than that of Au and Ag under AM1.5 illumination with the same geometry parameter. The light absorption enhancement after introducing Al nanopheres is optimized by nanosphere size, period and position being placed either on top (case I), in perovskite layer (case II), or simultaneously on top and in perovskite layer (case III), which mechanism isdiscussed in terms of the corresponding electric field and power loss density distributions. The maximal light absorption enhancement is revealed to ∼1.41 fold that of without Al nanosphere case. The SiO2, Al2O3 and TiO2 dielectric-nanoshell encapsulating effects on incident light trapping ability and photocurrent of the above optimized case are discussed as well. The present work holds great promise for choosing appropriate plasmonic material, size, period and position to facilitate designing perovskite solar cells and photo detectors.

Broadband terahertz absorber based on Dirac semimetal with tunable working bandwidth

A broadband metamaterial absorber (MA) based on bulk Dirac semimetal (BDS) with the property that the working bandwidth can be tuned is proposed. By changing the pattern on the top layer, the working band is expanded from narrowband to broadband. Interestingly, the working band over 90% absorption can be continuously changed from 0 to 3.4 terahertz (THz) when the Fermi energy level (EF) varies from 10 to 80 meV. The absorption mechanism of this broadband and tunable absorber is demonstrated and verified by the impedance matching theory, electric field, and power loss density distributions. Moreover, the proposed absorber is robust to the incident angle θ from 0°to 50°. Due to the symmetry structure, the designed absorber achieved the excellent property of polarization insensitivity. This proposed tunable broadband absorber may have a potential application in THz imaging and optoelectronic devices.

Broadband tunable terahertz metasurface absorber based on complementary-wheel-shaped graphene

We present a simple design for a broadband tunable terahertz metasurface absorber (MSA), which is composed of a periodic array of complementary-wheel-shaped (CWS) graphene sheets and a lossy polyimide layer backed with a ground-plane. Numerical simulation results show that the absorbance of the proposed MSA achieves over 90% for the frequency range of 1.77 THz to 4.16 THz with the relative bandwidth of about 80.6% when E f = 1.0 eV, and the absorbance is up to 93.6% and 99.8% at 2.07 and 3.83 THz. The proposed MSA is polarization-insensitive and wide-angle for both transverse-electric (TE) and transverse-magnetic (TM) waves. Fabry-Perot interference theory is used to analyze the mechanism of the MSA, and the theoretical results are agreement well with simulations. The absorption performance of the MSA can be flexibly adjusted by changing the Fermi energy level of the graphene. The simulated absorbance of the MSA can be adjusted from 19% to nearly 100% by changing the E f from 0.1 eV to 1.0 eV, which is consistent well with theoretical calculation. In addition, absorption properties of the MSA are also can be adjusted by changing the geometrical parameters of the unit-cell structure. Due to its simple structure and strong tunability, the proposed MSA has potential application prospects in the fields of tunable filtering, detection, sensing and so on. • A broadband tunable terahertz metasurface absorber (MSA) was proposed. • The absorbance of MSA is greater than 90% from 1.77 THz to 4.16 THz with the relative bandwidth of about 80.6% when Fermi energy level Ef = 1.0 eV. • Physics origin of MSA is studied by field and power loss density distributions and Fabry-Perot interference theory. • The absorption performance of the proposed MSA can be adjusted by changing the Fermi energy level and structure parameters.

Broadband dynamically tunable terahertz absorber based on a Dirac semimetal.

In this paper, we propose a broadband tunable metamaterial absorber in the terahertz (THz) region. The absorber comprises a Dirac semimetal film, a dielectric layer, and a gold ground plane. Numerical results show that the absorptivity remains above 90% in the range from 5.7 THz to 8.4 THz when the Fermi level is 65 meV. By varying the Fermi energy of the Dirac semimetal film from 40 meV to 80 meV, the absorption bandwidth and absorption peaks can be dynamically tuned. To explain the mechanism of high absorption, the magnetic field, surface current, and power loss density distributions at different resonant frequencies were presented. Our work may have potential applications in various fields such as sensors, detectors, and photovoltaic devices in THz regions.

An ultra-wideband, polarization insensitive metamaterial absorber based on multiple resistive film layers with wide-incident-angle stability

AbstractIn this work, we propose a broadband, polarization-insensitive and wide incident angle stable metamaterial absorber (MA) based on the resistive film. The absorber consists of a three-layer structure with each layer of dielectric substrate printed with different shapes of resistive film. The multilayer structure not only extends the absorption bandwidth but also maintains high absorption under large wave incident angles. Numerical simulation shows that the absorptivity of a normal incident wave is above 90% in the frequency range 2.34–18.95 GHz, corresponding to a relative absorption bandwidth of 156%. Moreover, the whole MA structure has a total thickness of 11.3 mm, corresponding to 0.09 λ0 at its lowest absorption frequency. Due to the high symmetry of the structure, the absorber has good polarization insensitivity. In addition, for both transverse electric and transverse magnetic incidence, the proposed absorber achieves an absorptivity of more than 80% at incident angles of up to 45° and thus has good stability for wide incident angles. The absorption principle of the absorber is analyzed by the surface current and power loss density distribution. Parameter analysis is also performed for bandwidth optimization. Due to its advantages of wideband absorption with high efficiency, the proposed absorber has the potential to be applied to the energy-harvesting and electromagnetic stealth fields.

Wide-range frequency tunable absorber based on cross-groove metamaterials and graphene-sheet

In this paper, a dynamic tunable graphene and metamaterial absorber with a periodic structure, composed of graphene and cross groove medium, is proposed. The results show that the absorption efficiency of the absorber is close to 100%, and by changing the chemical potential from 0.4 eV to 0.8 eV, the absorption peak can be adjusted from 6.4 THz to 8.75 THz, from 13.1 THz to 17.85 THz. The simulated electric field and power loss density distribution reveal that the absorption mainly comes from the excitation of continuous surface plasmon resonance on graphene structure. In addition, the absorber is insensitive to polarization, because both transverse electric and transverse magnetic modes have the geometric rotational symmetry of the unit structure. Furthermore, the absorption characteristics of the absorber can be adjusted dynamically by changing the chemical potential of graphene. The simulated results shows that the absorptivity is sensitive to the incident angle of the THz wave, which means this material can be used as angle sensors in the future.

Design of the Broadband Metamaterial Absorber Based on Dispersed Carbon Fibers in Oblique Incidence

In this paper, a broadband double-layer metamaterial absorber (MMA) based on carbon fibers (CFs) is proposed, which consists of three basic elements. Firstly, the reflectivity of CFs double-layer MMA in normal incidence is analyzed, and compared to the copper double-layer MMA with same size, the simulated results show that it obtains better absorbing effect. With the increase of incident angle, the multi-frequency resonance is activated, leading to larger effective bandwidth. Moreover, when incident angle is between 55 and 70 degrees, the continuous absorption band above 85% can totally cover X and Ku microwave band. Meanwhile, when the EM frequency is at 6-7.5GHz, the change of incident angle hardly affects the absorbing performances of CFs double-layer MMA. A specimen of the CFs double-layer MMA was fabricated by the vacuum bag molding process to verify its effectiveness and the measured results fitted well with the simulated results. In order to discuss the mechanism of EM absorption, the distribution of E-fields and power loss density were monitored. The results indicate that incident angle effects the distribution of E-fields and the way of absorption to change the absorbing performances. The proposed MMA has potential application prospects in the structural and functional integration design of CFs.

Absorption Efficiency Enhancement of Organic Solar Cells by Double Grating Structure

A novel surface-plasmon-enhanced structure is proposed to improve the absorption efficiency of organic solar cells in this paper. The PEDOT:PSS-Ag light-trapping structure introduced allows light to be reflected multiple times between the multilayer films, increasing the optical path length of light in the device and the light absorption by the absorption layer. The Ag film in P3HT:PCBM absorption layer can induce surface plasmons, which can enhance the electromagnetic energy around Ag film, improving the light absorption ability of organic solar cells. Based on the finite element method, the COMSOL-RF module is used to simulate the designed structure, and the absorption efficiency, electric field mode distribution and total power loss density distribution at different structural parameters were obtained. The results reveal that the absorption efficiency is more than 80% in the wavelength range of 485 nm to 520 nm in TE mode and more than 85% in the wavelength range of 495 nm to 595 nm in TM mode, providing a reliable basis for the development of high-performance organic solar cells.

Perfect metamaterial absorber based on the circular or elliptical cavity with one side open in the terahertz region

ABSTRACT In this work, we present the analysis and design of a perfect metamaterial absorber (MA) based on the circular cavity with one side open in the terahertz region. This structure consists of a metal plate where one circular cavity with one side open is vertically placed on. Based on the circular-cavity-theory, a formula can be used to calculate the resonant frequency. In terms of normal incidence, the simulated results show that the MA has one resonance point on 6.674 THz, which is consistent with the calculated results. What’s more, we present the distribution of E-field, surface current distribution and power loss density distribution in the cavity, and use the standing wave theory and electric dipole to prove the physical mechanism of the perfect absorption. Finally, an MA based on elliptical cavity with one side open is also studied. These results verify the application of resonant cavities in the field of MA.

Magnetic Resonated Bilayer Square-Ring–Enabled Dual-Peak Metamaterial Absorber in P-Band

In order to investigate the effect of magnetic metal on the absorption performance of metamaterial absorber (MMA), a dual-peak MMA based on magnetic metal nickel is designed and demonstrated in the P-band (300–1000 MHz). Two-layer square-ring-metal resonator arrays and two-layer dielectric substrates are arranged alternately with each other to constitute the proposed dual-peak MMA backed with a reflective metal plate. The influences of copper or nickel metallic layers on the absorption coefficients are comparatively analyzed. For the nickel MMA, the dual-peak absorption coefficients of 99.82% and 99.09% are achieved at 394 MHz and 605 MHz, respectively. Moreover, the thickness of dual-peak MMA could be reduced to 9 mm by employing magnetic metal nickel. The physical mechanism of dual-peak absorption is illustrated by surface current distributions, magnetic field distributions and power loss density distributions. The relationship between the changes of geometric dimensions and the shift of peak absorption frequencies is ultimately discussed. These results could provide instructive guidance for realizing a thin dual-peak MMA in the P-band.