渔网电磁超介质左手通带的超常透射及其电场增强效应的数值研究

本文利用电磁场数值模拟方法研究了分布矩形孔阵列的"金属-电介质-金属"三明治渔网电磁超介质在其左手通带发生的超常透射现象和不同模式激发下的电场增强效应。结果证实左手通带紧邻的超常光学传输峰源于波导共振模式,利用超常传输效应可以有效降低电磁超介质的损耗,提高左手性能;波导共振模和左手通带对应的反对称磁模能够分别在孔洞和金属夹层区域激发超过11倍的增强电场,因此渔网电磁超介质结构在表面增强光谱和传感等方面也具有潜在应用价值。     

基于特异材料的非完美透镜成像

There is widespread and strong interest in trying to fabricate a metamaterial in which both the permittivity and permeability are equal to -1 in order to achieve sub-wavelength imaging. Several metamaterial constructs have been proposed with varying degrees of success because of inherent losses, limited bandwidth and scattering from the abstracted circuit elements constituting the artificial material itself. A further limitation is the need to capture evanescent components from the object to be imaged that ...     

Development and analysis of Crank‐Nicolson scheme for metamaterial Maxwell's equations on nonuniform rectangular grids

In this paper, we develop a fully implicit scheme on staggered grids to solve the Maxwell's equations when Drude metamaterial is involved. Unconditional stability and optimal error estimate of the scheme are proved. Numerical results are provided to support the theoretical analysis, and used to demonstrate the applicability of the scheme to simulate the complicated backward wave propagation phenomenon occurring in metamaterials.     

一种新型左手材料的设计和特性研究

通过对左手材料的理论分析,设计了一种宽频带左手材料结构单元.该结构单元由一个矩形闭合环和十字型结构构成的谐振器和金属线组合而成.这种新结构中的谐振器实现负磁导率,金属线实现负介电常量,经过合理的设计,可以在某一频段内使得磁导率和介电常量同时为负,即具有负的有效折射率和正的波阻抗.数值仿真结果表明:在其工作频段内存在一个通带并且在17.6～29.0 GHz频率范围内折射率实部为负,而虚部接近于零;同时在该频率范围内波阻抗实部大于零,从而说明了该左手材料具有左手特性.除此之外,相对左手带宽达到48.9％,远远优于传统的左手材料.     

基于宽边耦合螺旋结构的低频小型化极化不敏感超材料吸波体

设计、仿真并实验验证了基于宽边耦合螺旋结构的低频小型化超材料吸波体. 实验测试结果表明, 该超材料吸波体在1.39 GHz吸收率达到最大为98%, 其单元尺寸和总厚度均为6.8 mm, 约为1/32工作波长, 实现小型化窄带吸波. 由于吸波体中螺旋结构是旋转对称排列的, 因而其对垂直入射电磁波的极化方向是不敏感的. 此外, 该超材料吸波体对斜入射横电和横磁极化电磁波在60°时, 仍具有强吸收. 关键词： 超材料 吸波体 小型化     

The metamaterial analogue of electromagnetically induced transparency by dual-mode excitation of a symmetric resonator

Electromagnetically induced transparency （EIT） is obtained in a symmetric U-shaped metamaterial, which is at- tributed to the simultaneously excited dual modes in a single resonator under lateral incidence. A large group index accom- panied with a sharp EIT-like transparency window offers potential applications for slowing down light and sensing.     

Tunable zeroth-order resonator based on a ferrite metamaterial structure

This paper proposes a tunable zeroth-order resonator on a composite right/left-handed transmission line consisting of a transversely magnetized ferrite substrate periodically loaded by microstrip inductors. Based on the propagation theory of edge guided modes, the analysis procedure of this structure is introduced. The numerical results demonstrate the tunability of the resonant frequency by changing the DC bias magnetic field applied to the ferrite. In contrast to previous work, the proposed structure is easy to design and fabricate and does not require a chip component.     

Optically active Babinet planar metamaterial film for terahertz polarization manipulation

A planar Babinet‐inverted dimer metamaterial possessing strong optical activity is proposed and characterized. An original fabrication method to produce large area (up to several cm²) freely suspended flexible metallic membranes is implemented to fabricate the metamaterial. Its optical properties are characterized by terahertz time‐domain spectroscopy, revealing anisotropic transmission with high optical activity. A simple coupled resonator model is applied to explain the principal optical features of the dimers, with predictive power of positions and number of resonances through a parametrical model. The model is validated for correct polarization‐dependent quantitative results on the optical activity in transmission spectra. The fabrication method presented in this work as well as the slit dimer design has great potential for exploitation in terahertz optics.     

Exploration of amphoteric and negative refraction imaging of acoustic sources via active metamaterials

The present work describes the design of three flat superlens structures for acoustic source imaging and explores an active acoustic metamaterial (AAM) to realise such a design. The first two lenses are constructed via the coordinate transform method (CTM), and their constituent materials are anisotropic. The third lens consists of a material that has both a negative density and a negative bulk modulus. In these lenses, the quality of the images is “clear” and sharp; thus, the diffraction limit of classical lenses is overcome. Finally, a multi-control strategy is developed to achieve the desired parameters and to eliminate coupling effects in the AAM.     

Light transmission along a slab waveguide with a core of anisotropic metamaterial

We investigated the dispersion property of a slab waveguide with an anisotropic metamaterial core whose permittivity tensor is partially negative. The subwavelength guidance characteristics are presented based on the boundary conditions. The results show that, at some specific frequencies, many high-order modes can exist in present waveguide even with the thickness of the guiding core 10 times smaller than the working wavelength. It is also found that different orientations of the optical axis of the anisotropic core will lead to different dispersion of the guided modes. If the orientation of the optical axis is properly chosen, the guided modes show a transition from backward wave to a forward wave as the frequency increases. During this transition, the group velocity of some guided modes can approach zero. Since the anisotropic metamaterial we discuss here can be fabricated in GHz, near- and mid-infra-red frequencies, our result may find some applications in wave trapper, integrated optical and nanophotonic devices.