Role of shape of hole in transmission and negative refractive index of sandwiched metamaterials

Transmission and negative refractive index （NRI） of metal-dielectric-metal （MDM） sandwiched metamaterial perfo- rated with four kinds of shapes of holes are numerically studied. Results indicate that positions of all transmission peaks of these kinds of holes are sensitive to the shape of the hole. Under the same conditions, the circular hole can obtain the maximum NRI and the rectangular hole can obtain the maximum frequency bandwidth of NRI. Moreover, the figure of merit （FOM） of the circular hole is the maximum too. As a result, we can obtain a higher NRI and FOM metamaterial by drilling circular hole arrays on MDM metamaterial.

Role of filling medium of holes in the transmission and negative refractive index of metal–dielectric–metal sandwiched metamaterials

The transmission and negative refractive index(NRI) of metal–dielectric–metal sandwiched metamaterials perforated with di?erent filling media of holes are numerically studied. Results indicate that filling the appropriate medium in rectangular holes can enhance transmission. The NRI and frequency bandwidth of NRI decrease with increased relative permittivity of the filling medium. A stronger magnetic response that contributes to the dual NRI metamaterials is found.

A new class of negative refractive index transmission line

We propose a new class of negative refractive index transmission line in which ideal operational amplifiers are applied to form the periodically loaded negative-impedance-converted inductors and capacitors. The phase response of the new trans-mission line is opposite to that of a positive refractive index conventional transmission line. Unlike the existing negative refractive index transmission line,the new negative refractive index transmission line is non-dispersive and thus can lead to many novel applications such as designing new broadband devices.

Science Letters:Lattice type transmission line of negative refractive index

In this letter,we introduce a novel passive transmission line of negative refractive index(i.e.,left-handedness)based on identical symmetrical lattice type structures thus called "lattice type transmission line"(LT-TL).The dispersion characteristic and the transmission response of the proposed LT-TL are analyzed.While all the other left-handed passive transmission lines are of high pass,the present passive left-handed transmission line is of low pass.Compared with a conventional transmission line,the LT-TL has a phase shift of 180° in the entire wide pass-band.

Wider frequency domain for negative refraction index in a quantized composite right–left handed transmission line

The refraction index of the quantized lossy composite right-left handed transmission line（CRLH-TL） is deduced in the thermal coherence state. The results show that the negative refraction index（herein the left-handedness） can be implemented by the electric circuit dissipative factors（i.e., the resistances R and conductances G） in a higher frequency band（1.446 GHz≤ ω ≤ 15 GHz）, and flexibly adjusted by the left-handed circuit components（Cl, Ll） and the right-handed circuit components（Cr, Lr） at a lower frequency（ω = 0.995 GHz）. The flexible adjustment for left-handedness in a wider bandwidth will be significant for the microscale circuit design of the CRLH-TL and may make the theoretical preparation for its compact applications.

Negative Refractive Index Metamaterial Structure Using SRR by Incidenting the Light Horizontally

Metamaterial structure based on split ring resonators (SRR) is proposed in order to produce a negative refractive index. For this structure we have used a new approach, instead of applying light perpendicularly incident. We apply horizontally incident input waves. A model of SRR is used to understand the behavior and its affects. We calculate the S-parameters using S-parameter analysis and the results for transmission, refractive index, permeability and permittivity of the structure is induced. The negative refractive index is found to be significantly dependent upon the width of the continuous wire as well as gap between resonators. Moreover, we study the effect of lattice constant on the electromagnetic response of the structure. It is expected that this work will provide useful information for design and fabrication of metamaterials with negative refractive index for in-plane applications.

Low-Loss, Broadband and Tunable Negative Refractive Index Metamaterial

This paper report on a low-loss, broadband, and tunable negative refractive index metamaterial (NRIM) consisting of yttrium iron garnet (YIG) slabs and printed circuit boards (PCBs). The YIG slabs under an applied magnetic field provide a negative permeability and the PCBs provide a negative permittivity. The substrates of the PCBs decuple the interactions between the YIG slabs and wire array deposed on such substrates. The effective electromagnetic parameters of the NRIM and the conditions of exhibiting the negative refractive index character are analyzed theoretically. Then the negative transmission and negative refraction characters are investigated numerically and experimentally. The results indicate that the NRIM exhibits negative pass band within the X-band with a bandwidth of about 1 GHz and a peak transmission power of about - 2.5 dB. While changing the applied magnetic field from 2300 Oe to 2700 Oe, the measured pass band of NRIM shift from 8.42 GHz to 9.50 GHz with a 2.7 MHz/Oe step. The results open a sample way to fabricate the NRIM, further, the metamaterial cloak and absorber.

Optical Negative-Index Metamaterial Using CSRR by Incidenting the Light Horizontally at Near-Infrared Domain

Metamaterial structure based on cascaded split ring resonators (CSRR) is proposed in order to produce a negative refractive index in terahertz regime at near-infrared range. We have incident light horizontally instead of incidenting it perpendicular. We have measured the negative refractive index, permeability and permittivity by using the S-parameter analysis. Furthermore, it is found out that negative refractive index, permeability and permittivity are dependent upon the width of the wire and the gap between resonators at near-infrared range. This work will be helpful for the fabrication and design of double negative metamaterials structure having negative permeability, permittivity and negative refractive index for in plane applications.

Membrane-based acoustic metamaterial with near-zero refractive index

We investigate a one-dimensional acoustic metamaterial with a refractive index of near zero（RINZ） using an array of very thin elastic membranes located along a narrow waveguide pipe. The characteristics of the effective density, refractive index, and phase velocity of the metamaterial indicate that, at the resonant frequency fm, the metamaterial has zero mass density and a phase transmission that is nearly uniform. We present a mechanism for dramatic acoustic energy squeezing and anomalous acoustic transmission by connecting the metamaterial to a normal waveguide with a larger cross-section. It is shown that at a specific frequency f1, transmission enhancement and energy squeezing are achieved despite the strong geometrical mismatch between the metamaterial and the normal waveguide. Moreover, to confirm the energy transfer properties, the acoustic pressure distribution, acoustic wave reflection coefficient, and energy transmission coefficient are also calculated. These results prove that the RINZ metamaterial provides a new design method for acoustic energy squeezing,super coupling, wave front transformation, and acoustic wave filtering.

Bandwidth Enhancement of RMPA Using 2 Segment Labyrinth Metamaterial at THz

The past few years have been very eventful with respect to the evolution of the concept and implementation of “left-handed materials (LHMs)”. This paper elucidates antenna parameter optimization using 2 Segment Labyrinth metamaterial embedded in antenna substrate at high frequency (THz). Ansoft HFSS has been used to design and analyse the RMPA (rectangular microstrip patch antenna) with design frequency 9.55 THz and operating range of 8.55 THz to 10.55 THz having RT Duroid (εr = 2.33) as substrate material. Magnetic properties of labyrinth resonator have been used to mathematically demonstrate the negative refraction. Nicolson Ross Wier (NRW) method has been used to retrieve the material parameters from transmission and reflection coefficient. Upon incorporation, bandwidth widens to around 4% and VSWR improves by approx 1.5%.

Dual-band metamaterial with a windmill-like structure

A broadband negative refractive index metamaterial based on a windmill-like structure is proposed, and investigated numerically and experimentally at the microwave frequency range. From the numerical and experimental results, effect media parameters are retrieved, which clearly show that two broad frequency bands exist in which the permittivity and permeability are negative. The two negative bands are from 9.1 GHz to 10.5 GHz and from 12.05 GHz to 14.65 GHz respectively, and the negative bandwidth is 4 GHz. Due to the good bandwidth performance, the metallic cell with double negative property obtained in this paper is suitable for use in the design of multiband or broadband microwave devices.

A novel structure for a broadband left-handed metamaterial

A low absorptivity broadband negative refractive index metamaterial with a multi-gap split-ring and metallic cross （MSMC） structure is proposed and investigated numerically and experimentally in the microwave frequency range. The effective media parameters were retrieved from the numerical and experimental results, which clearly show that there exists a very wide frequency band where the permittivity and permeability are negative. The influence of the structure parameters on the magnetic response and the cut-off frequency of the negative permittivity are studied in detail. This metamaterial would have potential application in designing broadband microwave devices.

Design of Structural Left-handed Material based on Topology Optimization

An effective method to design structural Left-handed material（LHM） was proposed. A commercial finite element software HFSS and S-parameter retrieval method were used to determine the effective constitutive parameters of the metamaterials, and topology optimization technique was introduced to design the microstructure configurations of the materials with desired electromagnetic characteristics. The material considered was a periodic array of dielectric substrates attached with metal film pieces. By controlling the arrangements of the metal film pieces in the design domain, the potential microstructure with desired electromagnetic characteristics can be obtained finally. Two different LHMs were obtained with maximum bandwidth of negative refraction, and the experimental results show that negative refractive indices appear while the metamaterials have simultaneously negative permittivity and negative permeability. Topology optimization technique is found to be an effective tool for configuration design of LHMs.

孔型对金属-介质-金属三明治结构超材料的透射率和负折射率的影响(英文)

通过改变长方形孔的长度,利用数值模拟研究了金属-介质-金属三明治结构超材料的透射率,负折射(NRI)率和品质因数(FOM)等性质.研究结果表明,随着长方形孔的长度的增大,低频透射峰和最大透射峰都出现了红移现象.长方形孔的负折射率和负折射带宽则随着长方形孔的长度的增大而减小.这意味着可以通过调节金属-介质-金属三明治结构超材料的孔阵列的长度获得较高的透射率或者负折射率.这些结果为开发太赫兹范围的光电器件提供可能的理论.

共面负折射指数波导的电容缺陷对传输特性的影响

在实际负折射指数漏波天线加工中经常出现误差,文章研究了负折射指数漏波天线的电容缺陷对传输特性的影响。利用缺陷负折射指数理论,得出当电容缺陷刚引入时,传输特性变化极其明显,而电容缺陷变大时,传输特性变化将很小,因为间距的变化破坏了负折射指数漏波天线整体对称性。

Electrodynamics—Two Versions and One Problem

Based on two versions of Maxwell’s Equations we investigate the Poynting vector, the energy transport and the dispersion relation both for right- and left-handed systems. Furthermore, it is shown that the latter systems are necessarily dispersive in contrast to the former ones. In the end we discuss a published example where the mixing of expressions of both versions of Maxwell’s Equations leads to unphysical conclusions. The presentation demonstrates for students how flexible can be the work with different versions of electrodynamics but also how carefully one has to be thereby.

负折射率材料的实现模式及传输衰减分析

推导了均匀材料折射率完整的解析表达式,并基于此按照材料导磁性、导电性和介电性的不同情形讨论了电磁波的传输模式,结果表明材料的导磁性和介电性是负折射率的必要条件;进而得到了实现负折射率的3种可能情形,即磁导率和介电常数至少一个参数为负值,与此同时传输衰减上升为负折射率材料的新挑战;虽然材料的导电性不是负折射率的决定因素,但导电性与材料的传输衰减关系密切。此外也探讨了零折射率材料的凋落波传输模式。

含特异材料的微波全向滤波器设计仿真

电磁波在折射率为零的特异材料中传播时具有相位不变、波长无穷大、出射波传播方向垂直于出射界面的特点.由正常材料与特异材料交替排列组合成的光子晶体存在零平均折射率带隙,且带隙不随晶格尺度、入射角度和偏振而变化.这一特性可用于设计新型全向滤波器.本文利用复合左右手传输线理论设计滤波器,得到实验加工参数.

密度为零的零折射率声学超材料研究

以普通波导管内部嵌入弹性薄膜为基本单元结构,构造了零折射率声学超材料.研究表明,在频率为fm=453.64Hz时能实现等效质量密度为零的零折射率超材料.在零折射率超材料两端接上截面积较大的普通波导管构造了复合零折射率超材料,利用声传输线理论和声阻抗匹配理论,分析了该复合超材料中能量传输和轴向声压分布情况.理论和仿真结果表明:尽管在零折射率超材料与普通波导管之间存在极大的几何不匹配,系统在输入声波频率为fm和Fabry-Pérot(FP)共振频率时能实现声波完全传输,且在频率fm处具有相位超耦合和传输增强等特性.除此之外,当改变复合超材料中零折射率超材料的长度D和弯曲角度θ时,发现其在频率为fm时所具有的特性不变,而FP共振频率的大小会随零折射率超材料长度的变化而改变.

电感L和电容C加载传输线媒质负折射特性分析

建立了一般性二维分布网络的标量波动方程,导出了二维分布网络的电压分布、电流分布、x方向和z方向阻抗以及传播常数,并把这些结果应用到二维加载L,C传输线媒质(负折射率媒质)和未加载传输线媒质(正折射率媒质)。获得加载传输线媒质的物质参数并显示为负数。利用这些表达式来设计这两种媒质的电参数和适当的平面波激励,利用微波电路对入射角为60°的平面电压波入射到相对折射率为-3的正负传输线媒质界面上进行仿真。仿真结果显示,在界面上发生了负折射,从而验证了本推导公式的正确性。