Near-field light localization using subwavelength apertures incorporated with metamaterials

We report strong near-field electromagnetic localization by using subwavelength apertures and metamaterials that operate at microwave frequencies. We designed split ring resonators with distinct configurations in order to obtain extraordinary transmission results. Furthermore, we analyzed the field localization and focusing characteristics of the transmitted evanescent waves. The employed metamaterial configurations yielded an improvement on the transmission efficiency on the order of 27 dB and 50 dB for the deep subwavelength apertures. The metamaterial loaded apertures are considered as a total system that offered spot size conversion ratios as high as 7.12 and 9.11 for the corresponding metamaterial configurations. The proposed system is shown to intensify the electric fields of the source located in the near-field. It also narrows down the electromagnetic waves such that a full width at half maximum value of λ/29 is obtained.     

Composite medium with simultaneously negative permeability and permittivity

We demonstrate a composite medium, based on a periodic array of interspaced conducting nonmagnetic split ring resonators and continuous wires, that exhibits a frequency region in the microwave regime with simultaneously negative values of effective permeability &mgr;(eff)(omega) and permittivity varepsilon(eff)(omega). This structure forms a "left-handed" medium, for which it has been predicted that such phenomena as the Doppler effect, Cherenkov radiation, and even Snell's law are inverted. It is now possible through microwave experiments to test for these effects using this new metamaterial.     

Modelling metamaterial transmission lines: a review and recent developments

This review paper is devoted to the discussion and comparison of the lumped element equivalent circuit models of the different types of metamaterial transmission lines that have been proposed so far, namely the CL-loaded lines, and those lines based on the resonant type approach. The latter category comprises both artificial lines loaded with split ring resonators (SRRs), or related topologies, and metamaterial transmission lines based on complementary split ring resonators (CSRRs). It will be the main aim of this paper to clearly justify the circuit elements of the models (and link such elements to the line physics and topology), to compare the different lines to the light of these models, and to point out the advantages and drawbacks of the different metamaterial transmission lines. As long as metamaterial transmission lines are exhaustively used for the design of compact microwave and millimeter wave components with improved performance and/or based on new functionalities, and their synthesis is based on the lumped element equivalent circuits, this paper is of actual interest for RF/microwave engineers and in general to those readers involved in metamaterial research and applications.     

Lamellar model of the left-handed metamaterials composed of metallic split-ring resonators and wires

Left-handed materials composed of split ring resonators (SRRs) and wires are investigated in the viewpoint of lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials staked alternatively. Several configurations of the SRR-wire metamaterial are numerically simulated to confirm its left-handed response as an analogy to the ENG-MNG lamellar model.     

垂直入射条件下厚金属环结构的负磁导率与左手材料行为

用矩形波导法实验研究了微波垂直入射于具有一定厚度的金属铜圆环结构的微波电磁响应行为.结果表明,当金属铜环的厚度增加到一定值时,在中心频率为145GHz处出现透射禁带,并且相位在透射禁带处发生跃变.采用双各向异性媒质理论计算了铜圆环结构的磁导率随频率变化关系,在透射禁带处磁导率为负.对厚金属圆环与金属线一一对应组合的样品,微波沿环面垂直入射时测量到左手透射通带和相位超前,通带带宽达到15GHz,强度为-21dB. 关键词： 负磁导率 垂直入射     

一种新颖的变异开口谐振环双频带磁谐振特异材料

根据磁谐振等效电路原理,设计出了工作在X波段的基于变异开口谐振环(split ring resonators)结构的新型双频带磁谐振特异材料.由于内外环间具有弱耦合的优越特性,所提出的磁谐振特异材料的两个工作频点可以较为方便地调节.该研究成果为特异材料的多频带、宽带化提供有益的的研究思路和设计方法. 关键词： 磁谐振特异材料 双频带 弱耦合     

Peculiarities of propagation of electroinductive waves in magnetic metamaterials

The coupling of doubly split ring resonators in the GHz range has been experimentally, analytically, and numerically studied in order to design a metamaterial with dominant electrical coupling as a model of nanoscale metamaterials. An example of propagation of GHz electroinductive waves in a metamaterial is demonstrated.     

一种兼有高增益和宽带低散射特征的波导缝隙天线设计

设计了一种同时具备高增益和宽带低散射特征的波导缝隙天线.将蚀刻有互补开口谐振环的方形贴片人工磁导体正交布阵得到宽带低雷达截面积(RCS)反射屏并以之代替原天线的全金属反射板,通过优化反射屏的加载方式,在展宽天线工作频带、提高天线增益的同时,实现了宽频域范围内天线鼻锥方向RCS减缩.实测结果表明:加载低RCS反射屏的缝隙天线工作带宽增加了100 MHz,前向增益提高了3.2 dB,在5.52—6.63GHz范围内RCS减缩量达10 dB以上,减缩带宽达到20%.     

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     

Numerical simulations of negative-index refraction in a lamellar composite with alternating single negative layers

Negative-index refraction is demonstrated in a lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively. Based on the effective medium approximation, simultaneously negative effective permittivity and permeability of such a lamellar composite are obtained theoretically and further proven by full-wave simulations. Consequently, the renowned left-handed metamaterial comprising split ring resonators and wires is interpreted as an analogy of such ENG--MNG layers. In addition, beyond the effective medium approximation, the propagating field squeezed near the ENG/MNG interface is demonstrated to be left-handed surface waves with backward phase velocity.     

GHz magnetic response of split ring resonators

Measurements of engineered subwavelength microstructures can be designed to have positive or negative and μ at desired frequencies. We present transmission measurements of a metamaterial consisting of split ring resonators (SRR). Results for different polarizations and propagation directions are presented. The transmission shows a dip even for propagations perpendicular to the SRR plane, provided that the incident electric field is parallel to the sides of the split ring resonators (SRRs) which contain the cuts. The experimental results agree well with the theoretical calculations.     

非均匀缺陷环对微波左手材料的影响

以金属铜六边形开口谐振环(SRRs)与金属铜线的组合为结构单元，研究了三维左手材料中的 缺陷效应. 利用电路板刻蚀技术制备了左手材料样品，采用波导法测量了SRRs构成的点缺陷 和线缺陷对左手材料X波段（8—12 GHz）微波透射行为的影响. 实验结果表明，引入不同尺 寸SRRs构成的点缺陷，材料谐振峰强度下降，最多达6 dB，相当于原来的186%，谐振频率 移动，通频带宽在630—720 MHz范围变化；引入不同尺寸SRRs构成三种取向的线缺陷时，材 料谐振峰强度下降，最多达11 dB，相当于原来的34 关键词： 左手材料 缺陷效应     

交指电容加载的周期性对称负磁导率人工材料研究

利用二端口网络理论和弗洛奎定理, 详细分析了周期性对称磁谐振人工材料的相对布洛赫磁导率与散射矩阵参数的关系, 利用这个关系提取了四种形式的开口谐振环布洛赫磁导率. 全波仿真和磁导率数值提取结果表明, 在开口谐振环的开口处加载交指电容, 磁谐振频率将显著降低. 这些成果将为提取周期性人工材料的布洛赫磁导率提供理论依据, 同时为小型化磁谐振特异人工材料提供新的设计思路.     

Study of a microstrip antenna on anisotropic metamaterials

The annular ring microstrip antennas on metamaterial substrates are modeled and analyzed using full-wave analysis in conjunction with Ansoft HFSS^TM. The influence of the permeability tensor of the split ring resonator medium on the resonant characteristics of the antenna is considered. Numerical results for typical resonant frequency behavior and return loss are presented as function of the metamaterial properties and antenna structural parameters.     

Transient optical modulation properties in the terahertz metamaterial of split ring resonators

The ultrafast optical modulation properties of split ring resonators are characterized by utilizing optical pump-terahertz probe spectroscopy.The experimental results show that when the terahertz electric vector is perpendicular to the gap of the split ring resonator,resonant absorption can be quenched significantly under high pump excitation.However,when the terahertz electric vector is parallel to the gap,the resonant absorption is less sensitive to pump excitation due to the structural properties of the metamaterial.Our numerical simulations also demonstrate that the pump pulse significantly influences the split ring resonator current by generating carriers in the substrate.     

Metamaterial Superstrate and Electromagnetic Band-Gap Substrate for High Directive Antenna

A high directive planar antenna made from a metamaterial superstrate and an electromagnetic band-gap (EBG) substrate has been investigated. A patch antenna surrounded with EBG structures is used as the radiation source. The CST Microwave Studio is used for the simulation. The results show that the gain of the antenna with metamaterial is 21.6 dB at the operating frequency of 14.6 GHz. Compared with the patch feed with the same aperture size but without the metamaterial superstrate, the performance of the antenna is improved obviously and the gain increases about 12.4 dB.     

基于平面超材料的Fano谐振可调谐研究

基于两段相同金属分裂环谐振器构成的单层结构, 从理论及实验方面研究了平面超材料的可调谐Fano谐振. 实验测量了平面超材料对TE和TM入射波的电磁响应, 利用电磁波的入射角度控制Fano谐振的强度, 实现了谐振的开关特性, 谐振频率红移可达到21%. 基于有限元法给出了平面超材料的场分布, 强的正常色散表明平面超材料的电磁响应可类比经典电磁诱导透明现象, 仿真与实验结果相符合. 对称结构超材料Fano谐振的开/关特性为超材料性能的可调谐控制提供了有效途径.     

Electric field controlled cohesive symmetric hook-C shape inspired metamaterial for S-band application

In this paper, a split ring resonator (SRR) bounded new cohesive symmetric hook-C shaped unit cell is developed. The metamaterial has 4   ×  4-unit cell array, which is applicable for s-band application for its high bandwidth (S₂₁ < -10 dB) of 0.6 GHz and high effective medium ratio (EMR) 12.78. Commercially available electromagnetic simulator CST (Computer simulation technology) microwave studio has been utilized at 2.93 GHz resonance frequency in this investigation. The electric field of this design is also observed by modifying the design structure that shows effective results. The new developed hook-C shaped metamaterial is fabricated and measured to validate the simulation results, which is eligible for high performance in long distance communications. The proposed metamaterial is highly recommended to apply in Airport Surveillance Radar (ASR) system for its highly effective medium ratio and size miniaturization.     

S波段超材料完全吸收基板微带天线

设计了基于树枝状结构单元模型的完全吸波超材料,并将此树枝状结构完全吸波超材料作为微带天线的基板,制备了S波段超材料完全吸收基板微带天线,模拟和实验结果表明,窄带和宽带完全吸波超材料都可提高微带天线的定向性和增益,性能得到了明显改善.经过优化设计S波段超材料完全吸收基板微带天线的增益相比普通微带天线提高了1.8 dB,相当于有效辐射功率提高了51%.表明将完全吸波超材料作为天线的基板,可以明显改善天线性能. 关键词： 树枝状结构 微带天线 完全吸波材料 增益     

Experimental observation of true left-handed transmission peaks in metamaterials

We report true left-handed (LH) behavior in a composite metamaterial consisting of a periodically arranged split ring resonator (SRR) and wire structures. We demonstrate the magnetic resonance of the SRR structure by comparing the transmission spectra of SRRs with those of closed SRRs. We have confirmed experimentally that the effective plasma frequency of the LH material composed of SRRs and wires is lower than the plasma frequency of the wires. A well-defined LH transmission band with a peak value of -1.2 dB (-0.3 dB/cm) was obtained. The experimental results agree extremely well with the theoretical calculations.