Search Results (333)

Metamaterial absorbers in terahertz (THz) based bands have garnered significant attention for their potential applications in military stealth, terahertz imaging, and other fields. Nevertheless, the limited bandwidth, low absorption rate, and heavy weight greatly reduce the further development and wide application of terahertz absorbers. To solve these problems, we propose a polystyrene (PS)-based ultra-broadband metamaterial absorber integrated with a polyethylene terephthalate (PET) double-sided adhesive layer and a patterned indium tin oxide (ITO) film through the simulation method, which operates in the THz band. The electromagnetic wave absorption properties and underlying physical absorption mechanisms of the proposed metamaterial absorbers are comprehensively modeled and rigorously numerically simulated. The research demonstrates the metamaterial absorber can achieve absorption performance of over 90% for fully polarized incident waves in the ultra-wideband range of 1.2–10 THz, especially achieving perfect absorption characteristics of over 99.9% near 1.8–1.9 THz and 5.8–6.2 THz. The proposed absorber has a lightweight physical property of 0.7 kg/m² and polarization-insensitive characteristic, and it achieves a broad-angle that allows a range of incidence angles up to 60°. The simulation research results of this article provide theoretical support for the design of terahertz absorbers with ultra-wideband absorption characteristics. Full article

The growing need for lightweight, customizable electromagnetic wave absorbers with weather resistance in aerospace and electromagnetic compatibility applications motivates this study, which addresses the limitations of conventional materials in simultaneously achieving structural efficiency, broadband absorption, and environmental durability. We propose a fused deposition modeling (FDM)-based approach for fabricating lightweight wave-absorbing structures using acrylonitrile-styrene-acrylate (ASA)/multi-walled carbon nanotube (MWCNT) composites. Results demonstrate that CST Studio Suite simulations reveal a minimum reflection loss of −18.16 dB and an effective absorption bandwidth (RL < −10 dB) of 3.75 GHz for the 2 mm-thick composite plate when the MWCNT content is 2%. Through FDM fabrication and structural optimization, significant performance enhancements are achieved: The gradient honeycomb design with larger dimensions achieved an effective absorption bandwidth of 6.56 GHz and a minimum reflection loss of −32.60 dB. Meanwhile, the stacked stake structure exhibited a broader effective absorption bandwidth of 10.58 GHz, with its lowest reflection loss reaching −22.82 dB. This research provides innovative approaches for developing and manufacturing tailored lightweight electromagnetic wave-absorbing structures, which could be valuable for aerospace stealth technology and electromagnetic compatibility solutions. Full article

The proliferation of electromagnetic wave applications has accentuated electromagnetic pollution concerns, highlighting the critical importance of electromagnetic wave absorbers (EMA). This study proposes innovative I-Wrapped Package Lattice electromagnetic wave absorbers (IWP–EMA) based on the triply periodic minimal surface (TPMS) lattice structure. Through a rational design of porous gradient structures, broadband wave absorption was achieved while maintaining lightweight characteristics and mechanical robustness. The optimized three-dimensional configuration features a 20 mm thick gradient structure with a progressive relative density transition from 10% to 30%. Under normal incidence conditions, this gradient IWP–EMA basically achieves broadband absorption with a reflection loss below −10 dB across the 2–40 GHz frequency band, with absorption peaks below −19 dB, demonstrating good impedance-matching characteristics. Additionally, due to the complex interactions of electromagnetic waves within the structure, the proposed IWP–EMA achieves a wide-angle absorption range of 70° under Transverse Electric (TE) polarization and 70° under Transverse Magnetic (TM) polarization. The synergistic integration of the TPMS design and additive manufacturing technology employed in this study significantly expands the design space and application potential of electromagnetic absorption structures. Full article

Multilayer thin films composed of cobalt (Co), carbon (C), and chromium (Cr) possess promising electromagnetic properties, yet the combined Co–C–Cr system remains underexplored, particularly regarding its performance as a microwave absorber. Existing research has primarily focused on binary Co–C or Co–Cr compositions, leaving a critical knowledge gap in understanding how ternary multilayer architectures influence electromagnetic behavior. This study addresses this gap by investigating the structure, phase composition, and microwave absorption performance of Co–C–Cr multilayer coatings fabricated via magnetron sputtering onto porous silicon substrates. This study compares four-layer and eight-layer configurations to assess how multilayer architecture affects impedance matching, reflection coefficients, and absorption characteristics within the 8.2–12.4 GHz frequency range. Structural analyses using X-ray diffraction and transmission electron microscopy confirm the coexistence of amorphous and nanocrystalline phases, which enhance absorption through dielectric and magnetic loss mechanisms. Both experimental and simulated results show that increasing the number of layers improves impedance gradients and broadens the operational bandwidth. The eight-layer coatings demonstrate a more uniform absorption response, while four-layer structures exhibit sharper resonant minima. These findings advance the understanding of ternary multilayer systems and contribute to the development of frequency-selective surfaces and broadband microwave shielding materials. Full article

Electromagnetic wave (EMW) absorption materials are crucial for a wide range of applications, yet most existing materials suffer from complex fabrication and narrow absorption bands, particularly under harsh environmental conditions. In this study, we introduce a broadband metamaterial absorber based on Ti₃C₂O₂ MXene, a novel two-dimensional material that uniquely combines high electrical and metallic conductivity with hydrophilicity, biocompatibility, and an extensive surface area. Through advanced finite-difference time-domain (FDTD) simulations, the proposed absorber achieves over 95% absorption from 0.3 µm to 18 µm. Additionally, other MXene variants, including Ti₃C₂F₂ and Ti₃C₂(OH)₂, demonstrate robust absorption above 85%. This absorber not only outperforms previously reported structures in terms of efficiency and spectral coverage but also opens avenues for integration into applications such as infrared sensing, energy harvesting, wearable electronics, and Internet of Things (IoT) systems. Full article

Noise reduction for manufacturing enterprises is favorable for workers because it relieves occupational diseases and improves productivity. An acoustic metamaterial with parallel, unequal cavities is proposed and optimized, aiming to achieve an optimal broadband sound absorber in the low–frequency range with a limited total thickness. A theoretical model for the acoustic metamaterial of a hexagonal column with 6 triangular cavities and 12 right–angled trapezoidal cavities was established. The lengths of these embedded apertures were optimized using the particle swarm optimization algorithm, with initial parameters obtained from acoustic finite element simulation. Additionally, the impacts of manufacturing errors on different regions were analyzed. The experimental results prove that the proposed acoustic metamaterials can achieve an average absorption coefficient of 0.87 from 384 Hz to 667 Hz with a thickness of 50 mm, 0.83 from 265 Hz to 525 Hz with a thickness of 70 mm, and 0.82 from 156 Hz to 250 Hz with a thickness of 100 mm. The experimental validation demonstrates the accuracy of the finite element model and the effectiveness of the optimization algorithm. This extensible acoustic metamaterial, with excellent sound absorption performance in the low-frequency range, can be mass-produced and widely applied for noise control in industries. Full article

This study developed cholesteric liquid crystal broadband reflective films using zinc oxide nanoparticles (ZnO NPs) and homotriazine UV-absorbing dye (UV-1577) to enhance infrared shielding. Unlike benzotriazole-based UV absorber UV-327, which suffers from volatility and contamination, UV-1577 exhibits superior compatibility with liquid crystals, higher UV absorption efficiency, and enhanced processing stability due to its larger molecular structure. By synergizing UV-1577 with ZnO NPs, we achieved a gradient UV intensity distribution across the film thickness, inducing a pitch gradient that broadened the reflection bandwidth to 915 nm and surpassing the performance of previous systems using UV-327/ZnO NPs (<900 nm). We conducted a detailed examination of the factors influencing the reflective bandwidth. These included the UV-1577/ZnO NP ratio, the concentrations of the polymerizable monomer (RM257) and chiral dopant (R5011), along with polymerization temperature, UV irradiation intensity, and irradiation time. The resultant films demonstrated efficient ultraviolet shielding via the UV-1577/ZnO NPs collaboration and infrared shielding through the induced pitch gradient. This work presents a scalable strategy for energy-saving smart windows. Full article

Two-dimensional transition metal carbides/nitrides (MXenes) have shown potential in biosensors, cancer theranostics, microbiology, electromagnetic interference shielding, photothermal conversion, and thermal energy storage due to their unique electronic structure, ability to absorb a wide range of light, and tunable surface chemistry. In spite of the growing interest in MXenes, there are relatively few studies on their applications in phase-change materials for enhancing thermal conductivity and weak photo-responsiveness between 0 °C and 150 °C. Thus, this study aims to provide a current overview of recent developments, to examine how MXenes are made, and to outline the combined effects of different processes that can convert light into heat. This study illustrates the mechanisms that include enhanced broadband photon harvesting through localized surface plasmon resonance, electron–phonon coupling-mediated nonradiative relaxation, and interlayer phonon transport that optimizes thermal diffusion pathways. This study emphasizes that MXene-engineered 3D thermal networks can greatly improve energy storage and heat conversion, solving important problems with phase-change materials (PCMs), like poor heat conductivity and low responsiveness to light. This study also highlights the real-world issues of making MXene-based materials on a large scale, and suggests future research directions for using them in smart thermal management systems and solar thermal grid technologies. Full article

Photothermal conversion is a pivotal energy transformation mechanism in solar energy systems. Achieving high-efficiency and broadband photothermal conversion within the solar radiation spectrum holds strategic significance in driving the innovative development of renewable energy technologies. In this study, a transmission matrix method was employed to design an interference-type solar selective absorber based on multilayer Cr-SiO₂ planar films, successfully achieving an average absorption of 94% throughout the entire solar spectral range. Further analysis indicates that this newly designed absorber shows excellent absorption performance even at a relatively large incident angle (up to 60°). Additionally, the newly designed absorber demonstrates lower polarization sensitivity, enabling efficient operation under complicated incident conditions. With its simple fabrication process and ease of preparation, the proposed absorber holds substantial potential for applications in photothermal conversion fields such as solar thermal collectors. Full article

To extend the spectral utilisation of In₂S₃, an In₂S₃/C₃N₄ nanocomposite was prepared. The effects of different sulphur sources, electrodes, and bias voltages on the optoelectronic performance were examined. Photoelectric properties in response to light sources with wavelengths of 405, 532, 650, 780, 808, 980, and 1064 nm were investigated using Au electrodes and the carbon electrodes with 5B pencil drawings. This study shows that the aggregation states of the In₂S₃/C₃N₄ nanocomposite possess photocurrent switching responses in the broadband region of the light spectrum. Combining two types of partially visible light-absorbing material extends utilisation to the near-infrared region. Impurities or defects embody an electron-donating effect. Since the energy levels of defects or impurities with an electron-donating effect are close to the conduction band, low-energy lights (especially NIR) can be utilised. The non-equilibrium carrier concentration (photogenerated electrons) of the nanocomposites increases significantly under NIR photoexcitation conditions. Thus, photoconductive behaviour is manifested. A good photoelectric signal was still measured when zero bias was applied. This demonstrates self-powered photoelectric response characteristics. Different sulphur sources significantly affect the photoelectric performance, suggesting that they create different defects that affect charge transport and base current noise. It is believed that interfacial interactions in the In₂S₃/C₃N₄ nanocomposite create a built-in electric field that enhances the separation and transfer of electrons and holes produced by light stimulation. The presence of the built-in electric field also leads to energy band bending, which facilitates the utilisation of the light with longer wavelengths. This study provides a reference for multidisciplinary applications. Full article

Transition metal dichalcogenide (TMD) materials have demonstrated promising potential for applications in photodetection due to their tunable bandgaps, high carrier mobility, and strong light absorption capabilities. However, limited by their intrinsic bandgaps, TMDs are unable to efficiently absorb photons with energies below the bandgap, resulting in a significant attenuation of photoresponse in spectral regions beyond the bandgap. This inherently restricts their broadband photodetection performance. By introducing metasurface structures consisting of subwavelength optical elements, localized plasmon resonance effects can be exploited to overcome this absorption limitation, significantly enhancing the light absorption of TMD films. Additionally, the heterogeneous integration process between the metasurface and two-dimensional materials offers low-temperature compatibility advantages, effectively avoiding the limitations imposed by high-temperature doping processes in traditional semiconductor devices. Here, we systematically investigate metasurface-enhanced two-dimensional MoSe₂ photodetectors, demonstrating broadband responsivity extension into the mid-infrared spectrum via precise control of metasurface structural dimensions. The optimized device possesses a wide spectrum response ranging from 808 nm to 10 μm, and the responsivity (R) and specific detection rate (D*) under 4 μm illumination achieve 7.1 mA/W and 1.12 × 10⁸ Jones, respectively. Distinct metasurface configurations exhibit varying impacts on optical absorption characteristics and detection spectral ranges, providing experimental foundations for optimizing high-performance photodetectors. This work establishes a practical pathway for developing broadband optoelectronic devices through nanophotonic structure engineering. Full article

In this paper, we propose a multi-mode switchable ultra-wideband terahertz absorber based on patterned graphene and VO₂ by designing a graphene pattern composed of a large rectangle rotated 45° in the center and four identical small rectangles in the periphery, as well as a VO₂ layer pattern composed of four identical rectangular boxes and small rectangles embedded in the dielectric layer. VO₂ can regulate conductivity via temperature, the Fermi level of graphene depends on the external voltage, and the graphene layer and VO₂ layer produce resonance responses at different frequencies, resulting in high absorption. The proposed absorption microdevices have three modes: Mode 1 (2.52–4.52 THz), Mode 2 (3.91–9.66 THz), and Mode 3 (2.14–10 THz), which are low-band absorption, high-band absorption, and ultra-wideband absorption. At 2.96 THz in Mode 1, the absorption rate reaches 99.98%; at 8.04 THz in Mode 2, the absorption rate reaches 99.76%; at 5.04 THz in Mode 3, the absorption rate reaches 99.85%; and at 8.4 THz, the absorption rate reaches 99.76%. We explain the absorption mechanism by analyzing the electric field distribution and local plasma resonance, and reveal the high-performance absorption mechanism by using the relative impedance theory. In addition, absorption microdevices have the advantages of polarization insensitivity, incident angle insensitivity, multi-mode switching, ultra-wideband absorption, large manufacturing tolerance, etc., and have potential research and application value in electromagnetic stealth devices, filters and optical switches. Full article

This work presents a theoretical and numerical investigation of a switchable tri-functional terahertz metamaterial incorporating vanadium dioxide (VO₂) and photosensitive silicon. The selective absorption, broadband linear-to-linear polarization conversion, and dual-band asymmetric transmission (AT) can be realized by utilizing the phase transition characteristic of VO₂. When VO₂ behaves as a metal, the proposed metamaterial functions as a selective perfect absorber for x-polarized waves at 2.84 THz, while exhibiting near-zero absorption for y-polarized waves. When VO₂ is in its insulating state, the proposed metamaterial acts as a linear polarization converter, achieving a polarization conversion ratio exceeding 99% within the frequency range of 1.07 to 4.29 THz. Meanwhile, a dual-band AT effect can be simultaneously realized associated with the broadband near-perfect polarization conversion. Furthermore, the polarization conversion efficiency and AT can be actively modulated by adjusting the conductivity of the photosensitive silicon, offering a novel approach for realizing multifunctional terahertz devices. Full article

In this paper, we design an ultra-thin broadband transparent absorber based on indium tin oxide (ITO) film, and we choose polymethyl methacrylate (PMMA) high-transmittance dielectric sheet instead of the traditional dielectric sheet and polyethylene glycol terephthalate (PET) as the ITO film substrate. Simulation results indicate that the absorber achieves more than 90% absorption for positively incident electromagnetic waves in the broadband range of 5–21.15 GHz with a fractional bandwidth (FBW) of 123.5% and a thickness of 6.3 mm (0.105 λ_L, where λ_L is the wavelength at the lowest frequency). Meanwhile, this paper introduces the interference theory to explain the broadband absorption mechanism of the absorber, which makes up for the defect that the equivalent circuit model (ECM) method cannot analyze the oblique incidence electromagnetic wave. This paper also compares the HFSS simulation results, ECM theoretical values, and interference theoretical values under positively incident electromagnetic waves to clarify the advantages of interference theory in the design of wave absorbers. Full article

Long-wave infrared (LWIR) broadband absorption is of great significance in science and technology. The electromagnetic field energy is absorbed by the metamaterials material, leading to the enhanced light absorption, from which the Metal–Dielectric–Metal (MDM) structure is designed. FDTD simulation calculation indicate that the bandwidth within which the absorber absorption ratio greater than 90% is 11.04 μm, and the average absorption rate (9.10~20.14 μm) is 93.6%, which can be accounted for by the impedance matching theory. Upon the matching of the impedance of the metamaterial absorber with the impedance of the incident light, the light reflection is reduced to a minimum, and increase the absorption ratio. Meanwhile, the good incidence angle unsensitivity due to the metasurface structural symmetry and the characteristics of the electromagnetic field distribution at different incidence angles. Due to the form regularity of the nanoring–nanowire metasurface structure, the light acts similar in different polarization directions, and the surface plasmon resonance plays a key role. Using FDTD electromagnetic field analysis to visualize the electric field and magnetic field strength distribution within the absorber, the electromagnetic field at the interface in the nanoring–nanowire metasurface structure, promote the surface plasmon resonance and interaction with damaged materials, and improve the light absorption efficiency. Moreover, the different microstructures and the electrical and optical properties of different top materials affect the light absorption. Meanwhile, adjusting the absorption layer thickness and periodic geometry parameters will also change the absorption spectrum. The absorber has high practical value in thermal electronic devices, infrared imaging, and thermal detection. Full article