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.

From electromagnetic bandgap to left-handed metamaterials:modelling and applications

In this paper, numerical modelling of left-handed materials （LHMs） is presented using in-house and commercial software packages. Approaches used include the finite-difference time-domain （FDTD） method, finite element method （FEM） and method of moments （MoMs）. Numerical simulation includes verification of negative refraction and ＂perfect lenses＂ construction, investigation of evanescent wave behaviour in layered LHMs, reversed Shell＇s Law in electromagnetic band gap （EBG）-like structures and construction of LHMs using modified split ring resonators （SRRs）. Numerical results were verified to be in good agreement with theory, At the end of this paper, potential applications of LHMs in microwave engineering are discussed.

Left-handed materials in magnetized metallic magnetic thin films

The authors＇ theoretical investigation on the high-frequency response of magnetized metallic magnetic films showed that magnetic films may become left-handed materials （LHMs） near the ferromagnetic resonance frequency of incident waves with right-handed circular polarization （RCP） and linear polarization （LP）. The frequency range where LHM exists depends on the waves polarization, the magnetic damping coefficient, and the ferromagnetic characteristic frequency corn of the film. There also exists a critical damping coefficient ac, above which the left-handed properties disappear completely.

TM modes in asymmetric slab waveguides with left-handed material

Three-layer slab waveguide with left-handed materials （LHM） is discussed using the Maxwell＇s equations and their equations of dispersion relation for TM modes are obtained. By seeking the power of the slab waveguide, their equations of effective thickness for TM modes are obtained. Furthermore, the interrelated equations for right-handed materials （RHM） slab waveguide are introduced and their curves plotted. To find new properties for LHM slab waveguide, the equations and their curves for the LHM and RHM slab waveguide are compared respectively.

Transmission properties of fractal Cantor distribution with left-handed materials

Transmission properties of fractal Cantor distribution with left-handed materials （LHM） are investigated. The transmittance and reflectance spectra can be calculated by using the optical transmission matrix method. Comparing with the conventional Cantor multilayers, these structures with LHM have double functions of stopbands and defects. Through adjusting the thickness of dielectric layers, the properties of stopbands and defects can be obtained, respectively. For stopbands, a broad stopband filter is studied. For defect modes, multi-frequencies narrow passband filters are proposed.

Higher order implicit CNDG-PML algorithm for left-handed materials

By incorporating the higher order concept,the piecewise linear recursive convolution(PLRC)method and CrankNicolson Douglas-Gunn(CNDG)algorithm,the unconditionally stable complex frequency shifted nearly perfectly matched layer(CFS-NPML)is proposed to terminate the left-handed material(LHM)domain.The proposed scheme takes advantages of CFSNPML formulation,the higher order concept PLRC method and the unconditionally stable CNDG algorithm in terms of absorbing performance,computational efficiency,calculation accuracy and convenient implementation.A numerical example is carried out to demonstrate the effectiveness and efficiency of the proposed scheme.The results indicate that the proposed scheme can not only have considerable absorbing performance but also maintain the unconditional stability of the algorithm with the enlargement of time steps.

Transmission line realization of subwavelength resonator formed by a pair of conventional and LHM slabs

In this paper, the authors present the transmission line (TL) realization of one-dimensional subwavelength resonator formed by a pair of conventional right-handed material (RHM) and left-handed material (LHM). In such resonator, a novel reso- nant mode with the resonant frequency depending on the length ratio of the RH/LH TL sections occurs as a consequence of the full phase compensation due to the backward wave in the LH TL section. The theoretical circuit-model analyses are supported by simulation and experimental evidence on resonators with different RH/LH length ratios.

负折射率介质中能流传输研究

研究了平面电磁波从各向同性且均匀的右手介质(ε(ω)>0,μ(ω)>0)透射到各向同性且均匀色散的左手介质中(ε(ω)<0,μ(ω)<0)的传播规律.通过场和坡印亭矢量的表达式,计算了坡印亭矢量对时间的平均值.从能流的角度,证明了电磁波从右手介质进入左手介质中时电磁波是以负角度折射的,并进一步推算了在Drude介质中的群速度,证实了群速度vg(ω)>0.

负折射率研究中的若干理论问题

对负折射率研究的理论作了评述,5年前美国UCSD的实验已证明用左手化媒质(LHM)确实可造成负折射。给出了一些理论预期,如负的群折射、负能量等。考虑了两个要点,一是正相速与负群速同时出现的可能,二是负相速与负群速同时出现的可能。认为现在已有多个负群速实验结果这一情况表明,P．M．Val- anju等在2002年5月发表的文章并不正确。实际上,在实验室中获取负群速并不困难。最后讨论了从测得的微波网络参数计算等效介电常数和等效导磁率的问题。

How to realize a negative refractive index material at the atomic level in an optical frequency range?

The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under certain conditions such a dense gas can exhibit simultaneously negative permittivity and negative permeability, and negligibly small loss.

Theoretical Investigation of Negative Refraction in Metallic and Ferromagnetic Composites

A new design of LHM (left-handed material) is suggested, in which the wave vectork and the energy flowS (the Poynting vector) are in the opposite direction. Metallic cores or lines are coated with ferromagnetic layers to obtain negative permittivity and permeability. This design may bring some improvements over the binary design, such as higher homogeneity, smaller volume size, lower power loss, higher convenience and economy. The analytical expressions for the permittivity ε and permeability μ are shown to be negative in certain direction and frequency regions. Two specific structures are theoretically discussed and proved to be left-handed. Key words left-handed materials - negative refraction - NIM - LHM - artificial crystal CLC number O 438 Foundation item: Supported by the National Natural Science Foundation of China (10344002)Biography: SU Hua (1978-), male, Master candidate, research direction: information optics.

微波异常传播中的负折射率问题

给出关于电磁波折射率理论的评述 .重点介绍了美国圣迭戈加州大学 (UCSD)研究组关于负折射率的实验 .该实验证明左手化物质 (LHM)