An ultra-broadband metamaterial absorber based on the hybrid materials in the visible region

In this paper, an ultra-broadband metamaterial absorber is successfully designed in the visible region. The structure of the absorber is just obtained by the two-dimensional plane structure which rotate 90° along x-axis. Furthermore, the formation of the structure for the hybrid materials is based on the four U-shaped structure of the metal titanium is embedded in the semiconductor (indium antimonide). The simulated results show that the proposed metamaterial absorber can achieve an ultra-broadband absorption with greater than 90% from 252.2 to 822.3 THz, and the relative absorption bandwidth gets to 106.1%. Finally, the simulated electric field, surface current and power loss density distributions further illustrate the absorption mechanism of the metamaterial absorber. And we believe the metamaterial absorber will have many potential applications in energy harvesting and stealth devices.     

Broadband metamaterial absorber on a single-layer ultrathin substrate

In this article, a broadband metamaterial microwave absorber on a low-cost FR-4 Epoxy substrate is proposed. The unit cell of the absorber consists of a staircase shape metallic patch placed on the top of the metal-backed ultrathin dielectric substrate having a thickness of 1.9 mm (0.07 λ₀). The absorption of more than 90% is achieved with this proposed low profile single-layer microwave absorber throughout the operation band from 8.86 to 15.5 GHz. The performance is analyzed for different values of incident angle, polarization angle, substrate height, and dielectric constant. The surface current and the power loss density at the top and bottom planes at the two absorption peaks of 9.46 and 13.90 GHz are also analyzed to elaborate the absorption mechanism of the structure. Experimental result closely follows the simulated one. The broadband characteristics of the design with relative absorption bandwidth (RAB) of 54.51% at both TE and TM polarizations of incident wave for a wide incident angles makes it versatile for applications in the X and Ku bands of microwave frequencies. The proposed work is very compact (unit cell size: 0.22 λ₀) with ultrathin substrate height (0.07 λ₀) and giving RAB performance of 54.51% comparable with that of others. Thus with this single-layer low-cost substrate material a broadband absorber is achieved.     

Broadband LWIR and MWIR absorber by trapezoid multilayered grating and SiO<Subscript>2</Subscript> hybrid structures

A broadband metamaterial absorber with high absorption simultaneously in mid-wave infrared (MWIR) and long-wave infrared (LWIR) was proposed. In the MWIR, the absorption higher than 0.8 is from 4 to 6.3 µm, while the absorption in the LWIR is from 8.7 and 9.6 µm. The absorber is insensitive to the incident angle. The broadband absorption in the MWIR is due to the slow-light effect of the trapezoid multilayered grating structure. And the broadband absorption in the LWIR is due to the phonon polariton resonant of trapezoid SiO₂ layer. In the broadband high absorption region, the atmosphere is transparent, which may greatly promote the practical application of the absorber in double-color IR imaging, detecting, infrared stealth and thermal emitting.     

Polarization-Independent Broadband Optical Regime Metamaterial Absorber for Solar Harvesting: A Numerical Approach

In this article, a broadband metamaterial (MTM) absorber is proposed that exhibits near-unity absorption in the terahertz regime. The proposed metamaterial absorber was initiated on a quartz (fused) substrate, whereas the resonator and backplane are constructed with tungsten. The resonator is designed with a square ring loaded with a face-to-face E structure at the center. It also consists of diagonally extended arrow-like shapes loaded from the corners and a concave-shaped structure extended from the middle of the square ring. Near-perfect absorption is observed at the frequencies of 465.2 THz, 585.2 THz, 648.8 THz, and 762.8 THz with absorption peaks of 99.8%, 99.9%, 99.92%, and 99.92%, respectively. Moreover, it exhibits broadband absorption properties above 90% absorption with bandwidths 20.4 THz, 80.8 THz, 41.6 THz, and 90 THz, respectively, at these resonance frequencies. Due to its symmetrical structure, it shows polarization-insensitivity behavior up to 90° with maximum absorption greater than 90% both in transverse (TE) and transverse magnetic (TM) modes. It also exhibits insensitivity to changes of incident angle from 0°–45°. Metamaterial properties of the proposed absorber are also analyzed, showing single negative behavior. Absorber property has been examined through surface current and equivalent circuit electric and magnetic field analysis. The effect of the cross-polarization is negligible and is verified through simulation. Due to its large bandwidth, polarization-insensitive behavior, and low PCR, the proposed MTM absorber can be incorporated into photovoltaic devices as a solar-energy harvester.     

基于圆台结构的超宽带极化不敏感太赫兹吸收器

本文提出一种基于圆台形吸收单元的超宽带、极化不敏感的超材料太赫兹吸收器. 该超材料吸收器采用金属薄膜金和介质层二氧化硅交替叠加的多层结构. 采用商业软件CST Studio Suite 2009时域求解器计算了其在0–10 THz波段内的吸收率A（ω）,在2–10 THz之间实现了对入射太赫兹波的超宽频带强吸收. 仿真结果表明,由于其圆台形单元结构,在器件垂直方向上形成一系列不同尺寸的微型吸收器,产生了吸收频点相连的多频吸收峰. 利用不同吸收峰的耦合叠加效应,获得超过8 THz的超宽带太赫兹波吸收,吸收强度达到92.3%以上. 这一结构具有超宽带强吸收,360°极化不敏感以及易于加工等优越特性,因而在太赫兹波探测器、光谱成像以及隐身技术方面具有潜在的应用. 关键词： 太赫兹波 超材料吸收器 圆台结构 超宽带     

一种基于3D打印技术的结构型宽频吸波超材料

设计了一种三层宽频吸波超材料,其表层和中间层为单元尺寸不同的周期阵列结构,底层为吸波平板结构,优化后的总厚度仅为4.7 mm,并采用三维(3D)打印技术成功制备了该吸波超材料.吸波体反射率测试结果表明,在电磁波垂直入射条件下,宽频吸收峰分别出现在5.3和14.1 GHz,两峰叠加使得其在4-18 GHz频率范围内反射损耗均小于-10 dB.采用S参数反演法计算了每一层的等效电磁参数,并利用多层结构反射率公式推导得出该模型的理论反射率,理论计算结果与实测结果基本一致.通过研究能量损耗、电场分布和磁场分布揭示了吸波机理,分析表明该吸波体的宽频吸收效果源于三层结构产生的吸收带宽叠加.本文提出的吸波超材料具有良好的宽频吸收效果,尤其在低频范围吸波性能较佳,结合3D打印快速成型技术,可获得结构精细的三层吸波超材料,具有重要的实际应用价值和广阔的应用前景.     

基于石墨烯和二氧化钒的太赫兹宽带可调谐超材料吸收器

太赫兹超材料吸收器作为一种重要的太赫兹功能器件,被广泛应用于生物医学传感、电磁隐身、军用雷达等多个领域.但这种传统的超材料吸收器结构具有可调谐性差、功能单一、性能指标不足等缺点,已经无法满足复杂多变的电磁环境的要求,因此可调谐超材料吸收器逐渐成为了太赫兹功能器件领域的研究热点.为实现超材料吸收器吸收特性的调谐,通常从调...     

An Infrared Metamaterial Broadband Absorber Based on a Simple Titanium Disk with High Absorption and a Tunable Spectral Absorption Band

A metamaterial absorber is proposed that functions in the medium- (3–5 µm) and long-wavelength (8–12 µm) infrared (medium-wavelength infrared, MWIR, and long-wavelength infrared, LWIR, respectively) regions. The proposed design, which consists of periodic cells, can be tuned to achieve single-band or dual-band light absorption by changing the periodicity of the structure. Each cell forming the metamaterial absorber consists of a bottom metal plate (Al), a top metal disk (Ti), and an intermediate dielectric medium (Si or ZnS) in which a metal disk (Ti) is embedded. For a period of 0.85 µm, the absorber achieves broadband absorption in the LWIR region, with an average absorption of 92.1%. Further, the absorber shows acceptable tolerance to irradiation at oblique incidence. For a period of 2 µm, a peak absorption of 99.05% is achieved in the MWIR region, thereby providing dual-band absorption. Tuning the periodicity of the structure enhances the localized surface plasmon resonance, with the absorption mechanism explained by establishing an equivalent parallel LC circuit. The absorption properties demonstrated by the proposed metamaterial absorber are promising for thermal imaging and infrared spectroscopy.     

极化控制的双波段宽带红外吸收器研究

红外吸收器在红外隐身、辐射制冷、红外探测、传感器等方面有重要的应用前景.一维光栅型吸收器由于其结构简单、易于加工的优势备受关注,然而其不足之处是频带很窄,且只对一种极化有效.本文提出了一种基于简单一维周期结构的双波段宽带吸收器,对横磁波和横电波都有效,且吸波频段随入射波的极化方式而改变.该结构的基本单元由八个梯度排列的子单元构成,每个子单元由两层金属-介质双层膜垂直层叠组成.全波仿真结果表明,在1.68—2μm波段,该结构对横磁波吸收超过90%,而对横电波吸收很小(小于6%);在3.8-3.9μm波段,该结构对横电波吸收超过90%,而对横磁波吸收很小(小于5%).另外,该结构具有宽角度吸收特性,当入射角增大到60°时仍然能够保持较高的吸收率和较宽的吸收频带.     

基于超材料的偏振不敏感太赫兹宽带吸波体设计

本文设计了一种基于超材料的偏振不敏感太赫兹宽带吸波体.吸波体包含两层金属和一层中间介质,表面金属层每一个周期单元由五种尺寸接近的金属块按照相邻不同的规律排列成5×5的方形阵列.各种尺寸金属块分别产生单峰谐振吸收,五个谐振吸收峰相互靠近从而产生宽带吸收.通过研究吸波体表面电流和电场z分量分布情况可知,入射太赫兹能量的吸收主要是由y方向上电场引起的电偶极子振荡和z方向上磁场引起的磁极化产生,而且金属层的欧姆损耗起主要作用.仿真结果表明,吸波体吸收率在80%以上的带宽约为1.2 THz,最高吸收率可达98.7%,半峰全宽(FWHM)为1.6 THz,该宽带吸波体的厚度约为中心波长的二十分之一,对偏振方向不敏感,且能实现大角度吸收,在太赫兹频段的电磁隐身、测辐射热探测器以及宽带通信等领域有潜在的应用价值.     

低雷达散射截面的超薄宽带完美吸波屏设计研究

提出了一种基于PMA单元结构的超薄宽带完美吸波屏设计方法. 该方法将多层拓展带宽的技术与单层多谐振方法有机结合, 实现带宽拓展的同时, 保持了完美吸波屏结构简单、无集总元件的特点, 易于实际加工和应用. 以双层三谐振超薄宽带完美吸波屏为例, 结合其等效电路, 理论上验证了所设计吸波屏的吸波机理, 同时验证了方法的有效性. 仿真分析该吸波屏具有低雷达散射截面、极化不敏感和宽入射角的特征. 仿真和实测结果表明: 该吸波屏在厚度为0.01 λ的条件下, 具有14.1%的半波功率带宽;-3 dBsm的雷达散射截面缩减带宽为18.9%, 在法线方向的最大缩减量为23 dBsm, 在法向±40°内具有较好的雷达散射截面减缩效果. 关键词： 完美吸波屏 宽带 雷达散射截面 等效电路     

Design of Broadband Metamaterial Absorbers for Permittivity Sensitivity and Solar Cell Application

A broadband and ultra-thin absorber for solar cell application is designed. The absorber consists of three layers,and the difference is that the four split ring resonators made of metal gold are encrusted in the gallium arsenide(GaAs) plane in the top layer. The simulated results show that a perfect absorption in the region from 481.2 to 684.0 THz can be obtained for either transverse electric or magnetic polarization wave due to the coupling effect between the material of GaAs and gold. The metamaterial is ultra-thin, having the total thickness of56 nm, which is less than one-tenth resonance wavelength, and the absorption coefflcients at the three resonance wavelengths are above 90%. Moreover, the effective medium theory, electric field and surface current distributions are adopted to explain the physical mechanism of the absorption, and the permittivity sensing applications are also discussed. As a result, the proposed structure can be used in many areas, such as solar cell, sensors, and integrated photodetectors.     

A polarization-dependent wide-angle three-dimensional metamaterial absorber

In this paper, a polarization-dependent wide-angle three-dimensional metamaterial absorber with a near-unity absorbance was presented. The metamaterial absorber structure is composed of coplanar electric and magnetic resonators. By carefully adjusting the structural dimensions, less-than-unity ε and/or μ can be realized. To match the impedance of free space, the structural dimensions were adjusted so that ε=μ, which guarantees minimum reflection. Since the resonance-based structure is made of metallic resonators and lossy substrates, the imaginary part of refractive index is large, which guarantees strong absorption of transmitted waves. Full-wave simulations confirmed the effectiveness of the proposed three-dimensional metamaterial absorber.     

基于电谐振单元的超介质吸波材料及矩形波导匹配终端应用研究

针对在自由空间中测试超介质吸波材料的高复杂性及高成本特点, 实验研究了4种由电谐振单元构成的超介质吸波材料在X波段(8–12 GHz)矩形波导里的吸波性能. 实验结果表明, 此4种吸波材料在终端短路的矩形波导里显示出与其在自由空间中相似的吸波性能及吸波机理.据此, 进一步研究了基于超介质吸波材料的矩形波导匹配终端应用. 分析结果显示, 此种新型匹配终端具有结构紧凑、工作频段可简单控制、成本低等优点. 通过展宽超介质吸波材料的吸波频段可设计出宽频带的矩形波导匹配终端. 关键词： 电谐振单元 超介质 吸波材料 匹配终端     

基于电阻型频率选择表面的低频宽带超材料吸波体的设计

基于电阻型频率选择表面(Resistance Frequency Selective Surface, RFSS) 设计了一种低频宽带、 极化不敏感和宽入射角特性的超材料吸波体. 该吸波体的基本单元由开槽十字型平面超材料(Cave Cross Planar Metamaterial, CCPM)、 RFSS、 电介质基板和金属背板组成. 采用FDTD方法数值模拟得到的结果表明: 相比于单纯的CCPM吸波体、 RFSS吸波体, CCPM和RFSS复合结构吸波体低频吸收特性得到极大改善, 在整个1-5 GHz频率范围内, 吸收率大于80%, 吸收峰值达到98%以上. 数值模拟得到的不同极化角和不同入射角下的吸收率表明: 该复合结构吸波体具有极化不敏感和宽角度吸收特性.     

Low-frequency and broadband metamaterial absorber based on lumped elements: design,characterization and experiment

In this paper, we propose and experimentally validate a low-frequency metamaterial absorber (MMA) based on lumped elements with broadband stronger absorptivity in the microwave regime. Compared with the electric resonator structure MMA, the composite MMA (CMMA) loaded with lumped elements has stronger absorptivity and nearly impedance-matched to the free space in a broadband frequency range. The simulated voltage in lumped elements and the absorbance under different substrate loss conditions indicate that incident electromagnetic wave energy is mainly transformed to electric energy in the absorption band with high efficiency and subsequently consumed by lumped resistors. Simulated surface current and power loss density distributions further clarify the mechanism underlying observed absorption. The CMMA also shows a polarization-insensitive and wide-angle strong absorption. Finally, we fabricate and measure the MMA and CMMA samples. The CMMA yields below ?10 dB reflectance from 2.85 to 5.31 GHz in the experiment, and the relative bandwidth is about 60.3 %. This low-frequency microwave absorber has potential applications in many martial fields.     

Broadband,polarization-insensitive,and wide-angle microwave absorber based on resistive film

A simple design of broadband metamaterial absorber(MA) based on resistive film is numerically presented in this paper.The unit cell of this absorber is composed of crossed rectangular rings-shaped resistive film,dielectric substrate,and continuous metal film.The simulated results indicate that the absorber obtains a 12.82-GHz-wide absorption from about 4.75 GHz to 17.57 GHz with absorptivity over 90% at normal incidence.Distribution of surface power loss density is illustrated to understand the intrinsic absorption mechanism of the structure.The proposed structure can work at wide polarization angles and wide angles of incidence for both transverse electric(TE) and transverse magnetic(TM) waves.Finally,the multi-reflection interference theory is involved to analyze and explain the broadband absorption mechanism at both normal and oblique incidence.Moreover,the polarization-insensitive feature is also investigated by using the interference model.It is seen that the simulated and calculated absorption rates agree fairly well with each other for the absorber.     

Broadband and ultra-low reflection metamaterial absorber embedded with magnetic materials

In this study, we design, prepare and characterize a broadband, ultra-low reflectivity and incidence angle-insensitive metamaterial absorber. The design of this absorber not only provides a novel idea for the design of broadband absorbers, but also enhances the application prospects of metamaterial absorbers. By introducing FeSiAlp/epoxy magnetic composite and optimizing the structural parameters, the absorption performance of the metamaterial absorber has been significantly improved. The effective absorption bandwidth (bandwidth with reflectivity less than −10dB) is increased by 3.4 times from 2.19 GHz to 7.49 GHz, and the RL_min (minimum reflection loss) value reaches −38.31 dB at 17.83 GHz, that is the absorption rate reaches 99.99%. Meanwhile, the experimental results also verify the simulation design results. Therefore, the absorber not only plays the characteristics of strong absorption of metamaterial, but also absorbs the advantages of broadband of magnetic material.     

超薄柔性透射型超构材料吸收器

设计并加工了一种超薄柔性透射型吸收器,总体厚度为0.288 mm,可实现柔性弯曲,容易做到与曲面目标共形.该吸收器由三层结构组成,底层是金属光栅,中间为介质层,表面单元由两条平行放置的尺寸不同的金属线组成.仿真和实验结果表明,对横电波在5和7 GHz的吸收分别达到97.5%和96.0%,对横磁波在3.0—6.5 GHz都能保持90%以上的透射率.两个吸收频点可分别独立调节,增加了设计的灵活性.另外,当入射角增大到60°时,该吸收器的性能基本不受影响,表现出良好的广角特性.     

Extremely-broad band metamaterial absorber for solar energy harvesting based on star shaped resonator

A new metamaterial absorber (MA) is investigated and shown numerically for solar energy harvesting for future solar cell applications. The structure consists of two metals and one dielectric layer having different thicknesses. Owing to this combination, the structure exhibits plasmonic resonance characteristics. In the entire spectrum of visible frequency region, the obtained results show that investigated structure has perfect absorptivity which is above 91.8%. Proposed structure also has 99.87% absorption at 613.94 THz and 99% absorption between 548 and 669 THz. The proposed structure also shows both polarization and angle independency for the entire visible region. The MA based solar cell proposes high absorption with an upper ratio of 90% in the widest range of visible spectrum comparing to the studies in literature. Hence, the proposed metamaterial absorber solar cells can be used for invisibility in entire spectrum of visible light. The absorption characteristics of the solar absorber are also investigated for infrared and ultraviolet region. The enhancement of absorption of the structure will provide new type of sensors in these frequency ranges.