新型八边形谐振环金属线复合周期结构左手材料奇异性质研究

通过实验及仿真研究了基于C环的新型八边形开口谐振环金属线复合周期结构左手材料.以金属铜八边形谐振环(SRRs)为基本单元的周期结构负磁导率材料,与闭口环(CSRRs)结果对比发现八边形谐振环能产生很好的谐振效果即能产生负磁导率;复合结构仿真结果显示,八边形谐振环金属线复合结构实现负折射具有可行性.设计、制作并实验和仿真研究了两种尺寸的八边形谐振环金属线复合周期结构左手材料,实验结果显示,分别在9.8—15 GHz和9.5—15 GHz出现良好负折射效应,表明小尺寸材料负折射频段较宽但整体能量透过率较小.通过与尺寸相近的传统C环样品实验对比发现八边形样品损耗较大,但其负折射区域能量分布比例较大,具有一定的优越性.该研究对新型周期结构左手材料的研究、设计和研制具有重要的科学意义,在国防、通信等领域也具有广阔的应用前景.     

新型八边形谐振环金属线复合周期结构左手材料奇异性质研究

通过实验及仿真研究了基于C环的新型八边形开口谐振环金属线复合周期结构左手材料.以金属铜八边形谐振环(SRRs)为基本单元的周期结构负磁导率材料,与闭口环(CSRRs)结果对比发现八边形谐振环能产生很好的谐振效果即能产生负磁导率;复合结构仿真结果显示,八边形谐振环金属线复合结构实现负折射具有可行性.设计、制作并实验和仿真研究了两种尺寸的八边形谐振环金属线复合周期结构左手材料,实验结果显示,分别在9.8—15GHz和9.5—15GHz出现良好负折射效应,表明小尺寸材料负折射频段较宽但整体能量透过率较小.通过与尺寸相近的传统C环样品实验对比发现八边形样品损耗较大,但其负折射区域能量分布比例较大,具有一定的优越性.该研究对新型周期结构左手材料的研究、设计和研制具有重要的科学意义,在国防、通信等领域也具有广阔的应用前景.     

结构参量对左手材料通带位置影响的研究

基于金属短板对和连续金属线(short-slab pair and continuous wires)复合结构,从理论上系统地研究了在THz波段结构参量对左手材料通带位置的影响.数值模拟结果表明,改变金属板宽度或厚度、连续金属线的长度或厚度都会引起左手材料通带位置向较高频段偏移. 关键词： 负折射 左手材料 结构参量 通带     

基于矩形谐振环的新型复合周期结构左手材料研究

通过实验及仿真研究了基于矩形谐振环的新型三角形和三矩形开口谐振环金属线复合周期结构左手材料.仿真研究了以金属铜三角谐振环和三矩形谐振环（SRRs）为基本单元的周期结构负磁导率材料,结果显示两种谐振环均能产生很好的谐振效果,即能产生负磁导率;设计、制作并实验和仿真研究了三角谐振环和三矩形谐振环金属线复合周期结构左手材料,实验结果分别在9.5—13.3GHz和9.8—12.5GHz出现良好的负折射效应,与仿真结果具有较好的一致性.该研究对新型周期结构左手材料的研究、设计和研制具有重要的科学意义和应用前景. 关键词： 左手材料 负折射 三角形谐振环 三矩形谐振环     

基于三角谐振环的新型六边形谐振环金属线复合周期结构左手材料性质研究

通过实验及仿真研究了三角谐振环组合新型六边形谐振环金属线复合周期结构左手材料.仿真研究了以金属铜三角开口谐振环（SRRs）为基本单元的周期结构负磁导率材料,与闭口环（CSRRs）结果对比发现三角开口谐振环能产生很好的谐振效果即能产生负磁导率,并且多层单元仿真发现多个谐振环耦合能提高谐振频率并加宽谐振频段;设计、制作并实验和仿真研究了三角开口环为基本单元的六边形谐振环金属线复合周期结构左手材料,仿真结果在98GHz附近出现良好负折射效应,实验验证在93—108 GHz出现良好负折射效应,与仿真结果具有良好的一致性.该研究对新型周期结构左手材料的研究、设计和研制具有重要的科学意义和应用前景. 关键词： 左手材料 三角环组成的六边形谐振环 负折射     

同时实现介电常数和磁导率为负的H型结构单元左手材料

基于用一种结构同时实现材料介电常数和磁导率为负的思想，提出了H型结构单元左手材料模型.采用矩形波导法测试表明，H型结构单元在微波频率范围出现左手透射峰，并且可以由参数t对左手特性区域进行调控.同时利用相位法、棱镜折射法和散射参量法从实验和理论证明了在左手透射峰区域材料的折射率为负值，介电常数和磁导率亦同时为负.相对由金属开口谐振环与金属线两种结构组合实现的左手材料，H型结构集磁谐振与电谐振于一体，结构简单、制备方便，对微波器件左手材料表现出更多的优越性.     

连通的开口和闭口谐振环构成的磁超材料设计

在已有的磁超材料和左手材料结构中,负等效磁导率主要通过开口谐振环、平行短金属线对或者它们的变形结构来实现. 这些结构要求入射电磁波的电场方向平行于基板. 针对这一特点,利用将开口和闭口的谐振环相连通的思想,设计出了入射电磁波的电场方向垂直于基板型的三维磁超材料,并予以实验验证. 该对称结构中金属线线宽的变化对磁谐振频率影响很小,有利于实际的加工和应用. 同时,该结构对于设计三维以及具有极化无关、均匀各向同性等特点的磁超材料和左手材料具有参考价值. 关键词： 磁超材料 谐振环 电场方向     

基于平行金属双柱的太赫兹波二维左手材料

基于产生负介电常数的周期性金属线单元结构,利用平行金属双柱设计了具有双负通带的两种太赫兹波段二维左手材料。应用时域有限积分算法研究了二维左手材料的传输特性,仿真结果表明,在0.76THz附近,平行金属双柱的表面电荷振荡与反向平行电流引发了电磁谐振,出现良好的负折射效应。在0.75～0.78THz之间同时具有负等效磁导率和负等效介电常数,双负通带带宽约为0.03THz。进一步研究了金属双柱间距、长度及基板厚度等结构参数对双负通带带宽的影响。研究结果为太赫兹波段左手材料的设计和研制提供了参考。     

双通带异向平板波导的特性

提出了一种基于平板波导的新型异向谐振结构——交叉椅型谐振结构,通过理论分析和数值计算,说明和验证了单个交叉椅型谐振结构加载的平板波导具有双通带特性和异向特性;设计了一种由多个交叉椅型谐振结构周期加载的异向平板波导结构,并通过仿真实验验证了其负折射特性。交叉椅型谐振结构的全金属半封闭式结构和其特殊的电磁谐振方式,使得此类2维异向平板波导与传统的由金属开口谐振环与金属线正交阵列而成的2维异向介质相比,具有双通带、无介质损耗、功率容量大等特异性质;单个交叉椅型谐振结构加载的平板波导作为一种新型的滤波器结构,具有良好的双通带特性,尺寸较小。     

非对称开口六边形谐振单环的微波透射特性

受自然界树型结构的启发，设计了分叉树型微结构单元，用电路板刻蚀技术制作了非对称开口六边形谐振单环及其组合结构.采用计算机模拟和实验研究了单个和多个谐振环在微波段(7—12 GHz)的电磁响应行为.研究结果表明：该结构具有负磁导率特性，开口谐振环几何尺寸影响环的磁谐振频率；两环环间距较小时出现二次谐振；带高级分支的辐射状环列相对于不带分支环列透射峰向低频移动.实验和模拟结果相符. 关键词： 负磁导率 开口谐振环 透射率     

Broadband planar left-handed metamaterials using split-ring resonator pairs

In this paper, we showed that split-ring resonator (SRR) pairs can be used as broadband planar left-handed metamaterials (LHMs). Simulations were carried out for one layer of infinite LHM slab using SRR pairs. The results showed that by carefully adjusting dimensions of the SRR pairs, magnetic and electric resonances can be coexistent at some frequency ranges and in the frequency range where there are both negative magnetic and electric responses, there is a broad LH band. Equivalent circuits for the magnetic and electric resonance were offered to give a qualitative and quantitative explanation of the LH behaviors of LHMs using SRR pairs.     

Parallel laser microfabrication of terahertz metamaterials and its polarization-dependent transmission property

Large-area split ring resonator (SRR) array was fabricated by femtosecond laser micro-lens array lithography at a fast speed. Transmission spectra of the SRR arrays at different incident terahertz wave polarization states were characterized by terahertz time domain spectroscopy. A polarization-dependent transmission property of the SRR array was observed. Polarization-dependent loss (PDL) spectrum was characterized to investigate the polarization properties of the terahertz metamaterials. The PDL characterization can eliminate the substrate effect and provide a flexible platform to study the characteristics of free-standing terahertz metamaterials.     

Electric and magnetic dipole couplings in split ring resonator metamaterials

In this paper, the electric and the magnetic dipole couplings between the outer and the inner rings of a single split ring resonator (SRR) are investigated. We numerically demonstrate that the magnetic resonance frequency can be substantially modified by changing the couplings of the electric and magnetic dipoles, and give a theoretical expression of the magnetic resonance frequency. The results in this work are expected to be conducive to a deeper understanding of the SRR and other similar metamaterials, and provide new guidance for complex metamaterials design with a tailored electromagnetic response.     

Fabrication of multilayer metamaterials by femtosecond laser‐induced forward‐transfer technique

A novel method based on femtosecond laser‐induced forward transfer for high‐throughput and efficient fabrication of periodic multilayer plasmonic metamaterials is demonstrated. With precisely controlling laser raster path applied on sputtered multilayer thin films, the laser‐ablated materials can be transferred to another substrate leaving the fabricated multilayer structure on the original substrate. Subsequently, three‐dimensional metamaterials can be made by multilayer structuring. Moreover, all the experimental results show that to create such multilayer split resonant rings (SRRs) with uniform profile, the laser fluence should be fine controlled under proper conditions. The optical property of fabricated multilayer SRR array is investigated by optical measurements and finite‐difference time‐domain simulations, showing various resonant modes in the middle‐IR region. The calculated induced current distributions exhibit rich resonance properties of the structures as well. This work markedly extends the laser direct writing technique to a wide application in fabricating complicated metamaterials and plasmonic devices efficiently.     

Amplitude- and phase-resolved optical near fields of split-ring-resonator-based metamaterials

We investigate the local optical response of split-ring resonator-(SRR)-based metamaterials with an apertureless scanning near-field optical microscope. By mapping the near fields of suitably resonant micrometer-sized SRRs in the near-infrared spectral region with an uncoated silicon tip, we obtain a spatial resolution of better than lambda/50. The experimental results confirm numerical predictions of the near-field excitations of SRRs. Combining experimental near-field optical studies with near- and far-field optical simulations provides a detailed understanding of resonance mechanisms in subwavelength structures and will facilitate an efficient approach to improved designs.     

Fabrication of terahertz metamaterials by laser printing

A laser printing technique was used to fabricate split-ring resonators (SRRs) on Si substrates for terahertz (THz) metamaterials and their resonance behavior evaluated by THz time-domain spectroscopy. The laser-printed Ag SRRs exhibited sharp edge definition and excellent thickness uniformity, which resulted in an electromagnetic response similar to that from identical Au SRR structures prepared by conventional photolithography. These results demonstrate that laser printing is a practical alternative to conventional photolithography for fabricating metamaterial structures at terahertz frequencies, since it allows their design to be easily modified and optimized.     

新型小型化的平面左手介质微带线及其后向波特性验证

基于裂缝谐振环结构的降频技术,首先设计了一种电尺寸较小的左手介质微带线单元,并根据电磁波在微带线上的传输和反射数据,分别计算了左手介质的有效介电常数和有效磁导率.之后针对左手介质八元阵列进行三维电磁仿真实验,结果表明该八元阵列在左手介质频段上具有独特的后向波效应,从而证实了该左手介质频段的存在.与传统的左手介质微带单元相比,阐述的左手介质单元的电尺寸减小了60%,而且结构简单,便于加工,适用于平面电路器件的小型化等应用研究工作. 关键词： 左手介质 小型化 双负特性 后向波特性     

一种基于开口谐振环的高增益端射天线设计

基于开口谐振环(split-ring resonator, SRR)奇异的电磁特性, 设计并制备了一种覆盖C和X波段的高增益SRR-Vivaldi端射天线. 采用等效分析方法对SRR结构谐振特性进行了研究, 并将其应用于传统Vivaldi天线指数渐变槽线前方, 使SRR结构形成特殊谐振能力的引向器, 将天线表面电流集中于端射方向, 在保证天线尺寸和带宽不变的前提下, 实现了天线增益的有效提升. 仿真和测试结果表明, 新型SRR-Vivaldi天线在C波段增益平均提高75.44%, xoy面和xoz面半功率波束宽度都缩减20°以上; 在X波段增益平均提高24.46%, xoz面半功率波束宽度大约缩减25°. 该结构具有低成本、设计简单、便于加工、利于共形等优点, 为端射天线提高增益和增强定向性提供了新思路.     

Magnetic response of split ring resonator metamaterials: From effective medium dispersion to photonic band gaps

On systematically investigating the electromagnetic response of periodic split-ring resonator (SRR) metamaterials as a function of the size-to-wavelength (a/λ) ratio, we find that the stop bands due to the geometric resonances of the SRR weaken with increasing (a/λ) ratio, and are eventually replaced by stop bands due to Bragg scattering. Our study traces the behaviour of SRR-based metamaterials as the resonance frequency increases and the wavelength of the radiation finally becomes comparable to the size of the unit cell of the metamaterial. In the intermediate stages, the dispersion of the SRR metamaterial can still be described as due to a localized magnetic resonances while Bragg scattering finally becomes the dominant phenomenon as a/λ∼1/2.     

Side branch-based acoustic metamaterials with a broad-band negative bulk modulus

We present theoretical investigations and numerical simulations of one-dimensional (1-D) acoustic metamaterials that exhibit wide negative bulk modulus bands down to zero. The metamaterials consist of double or quadruple branch openings in a 1-D waveguide. A lumped model is developed for theoretical analysis and the bandwidths of negative bulk modulus for different structures are calculated and compared. As much as 100 % increase over the traditional single branch opening structure in bandwidth can be achieved. The proposed metamaterials can be utilized to further achieve double negativity, which could facilitate applications such as acoustic cloaking and superlensing.