Waveguide design and application with transformation optics

Waveguide design becomes more and more important with the increasing demand of efficient routing and interconnection of electromagnetic signals for advanced information technologies. Here we review the basic theory, special techniques, and potential applications of transformation optics in waveguide design. Three major design strategies of transformation optics and their limitations in waveguide applications are discussed. The recent new trends of transformation techniques by imposing specific restrictions from materials are emphasized for practical implementation. Plasmonic waveguide is used as an example to compare these transformation strategies. Applications beyond waveguides but with great practical value such as super-resolution hyperlens design are also discussed in the context of waveguiding phenomena from the perspective of transformation optics.     

Thermal radiative properties of metamaterials and other nanostructured materials: A review

The ability to manufacture, control, and manipulate structures at extremely small scales is the hallmark of modern technologies, including microelectronics, MEMS/NEMS, and nano-biotechnology. Along with the advancement of microfabrication technology, more and more investigations have been performed in recent years to understand the influence of microstructures on radiative properties. The key to the enhancement of performance is through the modification of the reflection and transmission properties of electromagnetic waves and thermal emission spectra using one-, two-, or three-dimensional micro/nanostructures. This review focuses on recent developments in metamaterials-manmade materials with exotic optical properties, and other nanostructured materials, such as gratings and photonic crystals, for application in radiative energy transfer and energy conversion systems.     

Appropriate truncation for photonic crystals

Effective properties of one-dimensional photonic crystals in the resonance domain are investigated. The obtained analytic expressions of effective permittivity and permeability lead to several results. Firstly, in the case of lossless materials, effective permittivity and permeability take, in general, complex values. It is shown that these values are governed by the truncation of the boundary layer. Considering the particular case of a symmetric unit cell, the effective permittivity and permeability become purely real and, by the way, coherent with physics. Finally, in this case with a symmetric unit cell, we show that effective permittivity and permeability can stay nearly constant in a wide range of wavevectors including propagating and evanescent waves.     

一种宽角度极化不敏感的高可调谐红外超材料完美吸波体

提出了一种高度可调、宽角度且具有完美吸收和极化不敏感的超材料吸波体.模拟的结果显示, 在5.8μm处可达到最高吸收率99.9%;通过改变其几何参数, 吸波体的谐振波长在3.4μm到8.6μm的范围内可任意地调节, 且都具有不低于95%的峰值吸收率.在横磁波下, 当入射角度小于80°时, 吸波体的吸收率保持在95%以上;在横电波下, 当入射角小于60°时, 吸收率保持在92%以上.此外, 极化角度在0到90°变化时, 吸波体具有极化不敏感性.     

Improvement of 5.8 GHz Band Patch Antenna with Metamaterial

A patch antenna,a metamaterial patch antenna and a proposed metamaterial patch antenna,are simulated and compared.Simulation results show that the proposed antenna can concentrate so well radiation energy into broadside direction that the antenna gain is increased and the side lobe level is decreased.Therefore,the gain of the proposed metamaterial patch antenna is improved by 2 dB than that of the ordinary metamaterial patch anterma.     

基于微带传输线的由特异材料构成的一维光子晶体

通过左右手复合传输线(CRLH TLs)实现了一维的特异材料(Metamaterials),基于Metamaterials单元构成了光子晶体,并分析、测试了其传输特性.实验结果表明,由特异材料构成的一维光子晶体具有Bragg 带隙和等效的单负带隙.当晶格尺度同比例改变时,等效的单负带隙基本上不发生移动,并且带边分别由零平均介电常数ε-=0和零平均磁导率μ-=0决定.零平均折射率 (zero-n-)带隙和零有效相位(zero-Φeff)带隙可以理解为一种等效的单负带隙.对由Metamaterials构成的一维光子晶体传输特性的研究,有助于Metamaterials在射频/微波电路和仪器中的应用.     

Level set‐based topology optimization targeting dielectric resonator‐based composite right‐ and left‐handed transmission lines

In the last decade, metamaterials have been gaining attention and have been investigated because of their unique characteristics, which conventional materials do not have, such as negative refraction indexes. However, it is sometimes difficult to design metamaterials on the basis of experience and theoretical considerations because the relationship between their electromagnetic characteristics and structure is often vague. A mathematical structural design methodology targeting metamaterials may therefore be useful for expanding the engineering applications of metamaterials in industry. In this paper, a new level set‐based topology optimization method is proposed for designing composite right‐ and left‐handed transmission lines, each of which consists of a waveguide and periodically located dielectric resonators. Such transmission lines function as a fundamental metamaterial. In the proposed method, the shape and topology of the dielectric resonators are represented by the level set function, and topology optimization problems are formulated on the basis of the level set‐based representation. Copyright © 2011 John Wiley & Sons, Ltd.     

一种超宽带异向介质共面波导馈天线

基于裂缝谐振环的降频技术,利用色散性稳定、频带宽、电尺寸小的异向介质结构,设计了一种加载异向介质的新型平面波导馈天线（CPW-fed antenna）,实现了天线的宽带小型化。修正的PIFA传输线模型中,利用异向介质的谐振电路取代了传统辐射贴片不连续性而引起的电容效应。仿真和实测数据表明,该天线-10 dB相对带宽超过了80%,物理尺寸也缩减了近一倍,其谐振频段3.5～8.3 GHz内得到全向的辐射方向图。