Editorial for the Focus Issues on
Terahertz Metamaterials
Recent advances in metamaterials have enabled the Veselago prediction proposed nearly half a century ago to be realistic due to the introduction of subwavelength meta-atoms that possess unusual electromagnetic properties not found in nature, thereby showing fantastic phenomena, such as invisibility cloaking and superlensing, and great potentials for breakthrough device applications. Terahertz radiation (0.1–10 THz) is an intriguing electromagnetic wave that promises a wide variety of essential applications, particularly in sensing, imaging, communications, and spectroscopy. Recently, an exciting new field, terahertz metamaterials has emerged due to rapid development of both metamaterials and terahertz technologies. Being composed of periodically arranged unit cells of subwavelength dimensions, metamaterials are having the ability to tailor the flow of terahertz wave in a manner beyond what is possible with naturally occurring materials. It thus enables developing next-generation integrated terahertz devices and components with desired functionalities capable of being integrated into compact platforms for applications like aerospace communications, surveillance systems, terahertz imaging, sensing, and non-destructive detections.
The first part of the focus issue (published in Vol. 6, No. 1) contains five invited papers, while the second part here includes four invited papers, all of which are contributed by worldwide well-established experts in this area. We hope that the focus issue will stimulate the continuously rapid growth of terahertz metamaterials.
We are indebted to the Editor-in-Chief, Prof. Shenggang Liu, Academician of Chinese Academy of Sciences, for inviting us to serve as the guest editors for these important and timely focus issues. We also appreciate the Copy Editor, Miss Renbin Zhong, for her help in ensuring the timely production of the focus issues.
Finally, we appreciate all invited authors for their expert contributions.
The Guest Editors：
Tie Jun Cui, Ph.D.
Southeast University
State Key Laboratory of Millimeter Waves
Nanjing 210096, China
Phone: +86 13382760801
Email: tjcui@seu.edu.cn
Weili Zhang, Ph.D.
Tianjin University
Center for Terahertz Waves
Room 606, Building 26, Suite C
92 Weijin Road, Nankai District, Tianjin 300072, China
Phone: +86 22 2789 1015
Email: thztju@tju.edu.cn
TST, Vol. 6, No. 2, PP. 95-112
(Invited Paper) A partial-element analysis method for determining resonator coupling in terahertz metamaterials
John F. O’Hara 1*, Patrick L. Colestock 2, and Abul K. Azad 3
1 School of Electrical & Computer Engineering, Oklahoma State University
2 ISR-2, Los Alamos National Laboratory
3 Center for Integrated Nanotechnologies, Los Alamos National Laboratory
*1 Email: oharaj@okstate.edu
(Received May 2, 2013)
Abstract: Electric and magnetic coupling mechanisms between resonator elements are increasingly researched as additional tools to be leveraged in engineering the response in terahertz metamaterials. Full-wave simulations can reveal the overall effect of coupling on a metamaterial response but often leave questions about the relative strength of magnetic versus electric effects, and whether one or the other dominates the final response. This letter shows an analytical method called partial-element analysis to estimate and isolate the magnetic and electric interactions in metamaterial unit cells. Several case studies show the utility of the method for predicting resonance shifts in paired split-ring resonators. The extention of partial-element analysis to a more comprehensive simulation technique is briefly discussed and described as an optimistic direction for future analysis and engineering of nonlinear terahertz metamaterials.
Keywords: Metamaterials, Terahertz, Coupling, Magnetic, Electric
doi: 10.11906/TST.095-112.2013.06.06
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TST, Vol. 6, No. 2, PP. 113-124
(Invited Paper) Metamaterials design and challenges for THz radiation
Zhaoyun Duan 1, 2*, Su Xu 3, Hongsheng Chen 3, and Min Chen 4
1 Institute of High Energy Electronics, School of Physical Electronics, University of Electronic Science and technology of China, Chengdu 610054, China
2 Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
3 The Electromagnetics Academy at Zhejiang University and Department of Information Science & Electronic Engineering, Zhejiang University, Hangzhou 310027, China
4 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
*1 Email: zhyduan@uestc.edu.cn
(Received May 2, 2013)
Abstract: THz (Terahertz) radiation sources are an important research topic in THz science and technology. Novel THz radiation using double negative metamaterials (DNMs) and electron beam bunches is a promising candidate. In this review paper, we first introduce THz metamaterials, especially DNMs, including the design, fabrication and testing. Then we present our research progress on the enhanced THz radiation based on DNMs using single and multiple charged particles. Finally, we discuss the challenges in metamaterials and associated radiations. The research presented here offers theoretical and experimental foundations for developing new THz radiation sources.
Keywords: Double negative metamaterials, THz metamaterials, THz radiation, THz sources
doi: 10.11906/TST.113-124.2013.06.07
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TST, Vol. 6, No. 2, PP. 125-146
(Invited Paper) Transparent metals and inhomogeneous meta-surfaces
Zhengyong Song, Shiyi Xiao, Qiong He, Shulin Sun, and Lei Zhou *
State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education) and Physics Department, Fudan University, Shanghai 200433, China
* Email: phzhou@fudan.edu.cn
(Received May 2, 2013)
Abstract: We present a short overview on the research works related to two hot topics in metamaterials: transparent metals and inhomogeneous meta-surfaces. For the first topic, we first introduce a scattering-cancellation mechanism for making continuous metals optically transparent, and then propose a realistic design in optical domain, and finally experimentally prove the idea in both microwave and terahertz frequency domains. For the second topic, we show that light reflection/refraction at a carefully designed gradient-index meta-surface follows a generalized Snell’s law, and then demonstrate that such a system can perfectly convert a propagating electromagnetic wave to a surface wave under certain conditions, and finally introduce several interesting applications of this type of systems.
Keywords: Metamaterials, Transparent metal, Terahertz, Scattering cancellation mechanism.
doi: 10.11906/TST.125-146.2013.06.08
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TST, Vol. 6, No. 2, PP. 147-164
(Invited Paper) THz and microwave surface plasmon polaritons on ultrathin corrugated metallic strips
Tie Jun Cui * and Xiaopeng Shen
State Key Laboratory of Millimetre Waves, School of Information Science and Engineering, Southeast University, Nanjing 210096, China
* Email: tjcui@seu.edu.edu
(Received May 2, 2013)
Abstract: In the terahertz and microwave frequencies, natural surface plasmon polaritons (SPPs) do not exist, but can be supported by plasmonic metamaterials, which are usually periodic structures decorated on metallic surfaces. In this review paper, we introduce a kind of planar or flexible plasmonic metamaterial on thin metal films with nearly zero thickness. From theoretical simulations and experiments, we demonstrate that spoof SPPs can propagate along an ultrathin corrugated metallic strip and be highly sustained along two orthogonal directions of the strip in the terahertz and microwave regions with excellent performance, such as broadband, good modal shape, long propagation distance, and low bending loss. We also show that such ultrathin corrugated metallic strip can be printed on flexible dielectric film to support conformal surface plasmons (CSPs) on arbitrary surfaces. The ability to bend spoof SPPs freely makes the ultrathin plasmonic metamaterial more practical to produce plasmonic devices. We have designed and simulated broadband planar and flexible SPP waveguide, 90o bend, beam splitter, and ring resonator in the terahertz frequency, which exhibit excellent performance. Experiments in the microwave frequency validate the feasibility of the ultrathin plasmonic metamaterial.
Keywords: Terahertz metamaterials, Surface plasmon polaritons, Conformal surface plasmons, Plasmonic devices
doi: 10.11906/TST.147-164.2013.06.09
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