玄妙的电磁超材料 Magical EM Metamatetials (陈志宁)

Panda Chen

二零二二年四月二十八日

【问】陈老师：讨论一个超表面天线的概念，现在是否有一个趋势单元尺寸为三分之一个波长，甚至二分之一个波长的单元组成的平面阵列也称作超表面？这跟原来的超表面和超材料的定义有了较大偏差。

【陈】：是的。应该说，“超”更是一个“泛”，广义上的“超”，也是“泛滥”了。但是，其实，这种说法也没有越界。因为“超”的电磁结构有谐振和非谐振二种。谐振的从十分之一到四分之一甚至二分之一波长（在这里和FSS重叠了）。

【问】：发现FSS也归到超表面了

【陈】我个人觉得，是否“超”，主要还是要看，一，人工结构，二，特殊电磁性质，三，自然界还没有能够实现该性质的材料。【问】所以单元尺寸就被弱化了。

【陈】是的。这个是最初的定义。这轮超材料研究的最大贡献之一就是一个统一特殊或复杂电磁媒质框架。所以，我以为，“泛”或“超”材料不是严格的物理定义，更多的是一种说法。

二零二零年五月九日

细读IEEE TAP三月份 Special Issue on Recent Advances in Metamaterials and Metasurfaces特集的三位客座编辑的前言。文中对metamaterials和metasurface的简要回顾挺好的，尽管我不完全同意他们对metamaterials的定义。他们把metamaterials定义为“artifitial materials engineered...”。我觉得应该是“natural materials artificially engineered.. ”。

有意思的是，其中有一段评价Capasso教授的工作对metasurface研究的贡献。建议大家读读。这个评价既在相当程度上也是对光与微波在metamaterials工作上的评论，也是对光metamaterials研究自带光环（因为有光，哈哈，通常都在物理性期刊上发表）的质疑。事实是，许多光方面的工作的原始想法来源于微波早已成熟的工程工作，尽管真正的理论创新无所谓在那个频段。自一九四八年，Kock首创metamaterials，就是从微波透镜开始的（一个典型的工程设计驱动的理论创新的案例）。而五十年后，Pendry开创性地“救活”metamaterials也是从微波段工作开始的，论文发表在IEEE TMTT。然后，metamaterials逐渐被“炒”上了天（光相对微波段的频率之高如同天地之分）。平时，我也读/关注一些光学metamaterials的工作。通常，经常是，在读明白（对我而言不太容易）后，会有一种对基本理论似曾相识的感觉，除了更多的抽象的物理名词和更多一般意义上的解释（这个挺受益）。作为天上的光，论文可以发表在SN。而地上的微波，都发表在IEEE T（再次证明SN和IEEE T在原创性方面，旗鼓相当，关注点不同而已。）。

迄今为止，metamaterials的研究已再次火了二十年。“评论”说，已经来到了十字路口。我觉得这个对metamaterials的现状描述，对也不对。对于光metamaterials似乎是大潮已退，如同任何一次研究wave，退潮后的金色沙滩上，通常既留下来了几个大海星，大海螺，也留下来了不少裤衩。我以为，metamaterials的研究，如果不在工程技术上有所发展，恐怕就根本不存在一个所谓的十字路口了吧。比如，现在许多人已经转移到其他新的热点（赶新浪），或到EEE在发余光了。

一向被应用驱动的微波metamaterials天线技术研究与发展，则是方兴未艾。正所谓，metamaterials研究是，始于微波，益于微波，成于微波。

二零一九年十二月十四日深圳

自二零一零年以来，我和我的伙伴们一直致力于基于metamaterials/metasurface/metaline的天线研究，开发及应用，特别是竭尽全力地在业界普及和推广这个创新的机会。据不完全统计，在各种工业界的技术活动中的主旨报告三十余场，在各家公司研究所的报告超过二十多场。如苦行僧般，像祥林嫂似地推销技术，分享理念，期待天线业界在技术上的质的飞跃。

十年磨一剑，昨天非常欣慰地知道，metamaterial的概念与技术已经深入业界的人心。一位业界的领头羊自豪地告诉我：现在我们的新天线设计中，处处都能看到meta。是学术界的思想和理论促进了我们天线技术的飞速发展。听罢，对meta在业界的开花结果颇感欣慰。这应该是我们多年努力所要追求的目标，也是对一个技术理念的最高的评价。

二零一八年八月三十日于北京

自1999年以来，metamatetials作为一个尚在探索中的物理概念，已经得到了广泛而深入的研究。这一概念已经大大地拓展了，注意不是更新或突破了，原有的物理概念，所以理论界从一开始的怀疑与迟疑，到全身心地投入去研究探索了。然而，在另一方面，工程界对该概念的认知却严重滞后。许多时候，对这一概念的怀疑甚至否定仍然占据了主流。根据我的观察与分析，可能有以下几种原因。

一，因为根据metamaterials新的独特性质，传统的EM以及各种相关的技术几乎都有可能被大大得更新，以致许多人觉得不可思议。二，对什么是metamaterials不是很清楚。在没有真正地搞清什么是metamaterials的定义及涵盖的情形下，只凭几个常听到的名词如左手性材料，负折射率材料等就得出结论。三，因为大多数的研究还停留在理论探讨层面。没有把物理概念语言转换成工程设计参数，如S参数等，以致工程人员无法直接应用。四，在物理概念与工程技术及应用之间存在着巨大的鸿沟。五，尽管科学研究成果不断，但绝大多数还停留在概念和现象上，并没有解决工程应用中的关键问题或作为产品的所有指标。而现有的许多号称从事metamaterials产品开发的，要么挂羊头，卖狗肉。要么干脆就是皇帝的新装。严重地混淆视听，甚至污名了metamatetials相关技术发展和应用。

我们团队(包括新科技和新国大)经过多年的艰苦努力，特别是和工业界密切的互动，已经在物理概念的认知上，有了自己独特工程见解。在特别是天线技术解决方案设计上有了突破，在系统应用方面已经开始取得了成功。这些全新的进展都强烈地告诉我们，metamaterials不仅仅是一个理论上的新概念，更是天线技术创新的新机遇。

个人以为，如果没有新的概念的引入，一则，作为经历了百年发展的天线技术，如何创新以适应迅速发展的应用需求呢？再则，学术界和研究界又能为工业及应用奉献什么创新性的技术呢？

这个美篇，原本是写给我的学生们看的。通过收集了一些关于泛/元/超材料的基本信息以及我个人对泛材料的一些认识与感悟，希望能够向我的学生概述一下泛/元/超材料的概念，后被分享出去了，就借机与大家分享和探讨它的概念与应用了。

备注:

泛材料即metamatetials，这是一次在与师兄弟们讨论如何更准确地翻译这个新术语时，我提出的。大家觉得如何?当然，meta也有“元”和“超越”的意思。

一点注释：

自metamaterials被提起的第一天起，因为它打破了所有现有电磁场中物理概念的藩篱，非常自然地引起了许多争论。这种争论既是正常的，更是有益的。它大大地促进了该理论的发展与完善。

另一方面，在工程界也有很大的争议，而且这种争议并没有随着越来越多的应用的出现而减弱。原因不外乎，一是对概念，其实更多的是对表述上的不认可。二是还是缺乏的工程上成功的范例。三是没有分清科学和工程语言上的微妙区别。四是把物理概念等同于工程技术。五是没有机会真正搞明白那个概念，而是靠想像或所谓的直觉去理解。六是因为圈里的一些不实或泛美之词甚至一些学术界的江湖骗子的不齿所为。

我以为，作为工程技术研究人员的我们，最重要的是要努力明白科学语言和物理概念，然后努力把对物理概念的抽象的理论描述的科学语言转换成可设计的工程技术参数，从而架起应用与理论的桥梁。

另外，在讲述和推销这个概念时一定要客观，要分清你在和谁说话。在“忽悠”研究基金时，你可以也应该画一张梦幻之图，编一些新名词和时髦的术语，让大家憧憬。作为科学研究，就是去探索未知，就是要展开想像的翅膀。但当你谈论工程技术时，还是老老实实地把工程上的可行性放在前台，忘掉那些美妙的名词，扎扎实实地解决问题，来不得半点虚假。

搞工程技术的我，从来不参与所谓概念上的争论，那是搞物理人的事。我曾经经历过对MEI方法的争论，现在的META。对我而言，解决具体问题就是硬道理。一旦将概念成功地转化为技术，而技术又被市场采用了，就是真正的成功。至于，新技术被冠以了META,还是TAME重要吗？

众所周知，物理概念是工程技术的基础。任何一个新的物理概念都有可能会对技术发展产生革命性的影响。技术要创新，就必须密切关注物理概念的变化与发展。

其实，泛材料的研究发展的最大贡献或影响既是为技术创新打开了一扇窗，更是促使我们创新思维（think out of box），改变自己的世界观/哲学思维的意义更大。

关于metamaterial，metasurface and metaline

metamaterials应该是一个“泛”“元”“超

”或更广义的从材料特性上定义的描述，包括所有的维度结构，三维，二维和一维。

Natural materials artificially engineered to reveal exotic EM properties not yet found in nature.

metamaterials因为更关乎结构的材料特性，通常更多把它用来描述三维结构的独特电磁特性。

二维电磁结构或metasurfaces，则更多是从等效边界条件角度，谢昆诺夫，惠更斯等描述结构的独特电磁特性。

而一维电磁结构或metalines的方便的描述则是传输线模型。

从电磁的角度metamaterials只是具备等效电磁特性的结构，而不是真正材料科学与工程意义上的材料。对于材料科学与工程，一块木板，切到木屑它的材料特性不会变。把这个木头放在另外一个木头或金属上，它原来的材料特性不会变。而对EM而言，metamaterials在这二种情况下都会变。所以以“伪”材料称EM Metamaterials为是话粗，理不粗。(我更喜欢用泛材料)

Q&A

@赵宇 

把‘’超‘’换成‘’泛‘’更容易接受一些。

A:是的。超，在中文中很容易歧义。在英文中是superman和metaman的区别。前者还是人，尽管是非凡人，后者尽管有人形但就不是人了，如机器人/:,@P

Q:@白衣洛阳: 什么是超材料的精髓? 

A:它们的精髓就是可以人工地构造出自然材料所没有的电磁特性。

Q:@白衣洛阳: 陈老师，您好。其实我是想问，基于超材料，可以反衍出好介电常数或磁导率，或0折射。但是，所以可用于小型化，带宽增强。到是0折射是不是真的没有太多实际意义，我想不出其适用领悟。谢谢陈老师指正。[Joyful]

A: 谢谢你们。超材料，更准确的说，是泛材料，为天线创新开辟了一个新天地，但不是一个具体的技术更不是万能的狗皮膏药。所以，我们工程师的任务就是把抽象深奥的物理概念转化为解决具体问题的技术，最终转化为产品

勤讯 尧强

只是感觉超材料被xx这种玩坏了，而且跟材料科学的研究对象好像不一样吧

A:@王尧强-勤讯 林子大了什么鸟都会有。大浪淘沙啊😄 泛泛而谈是一样的，都是试图通过构造结构实现新的材料特性/增强现有的材料特性。但实现的方法上不同，物理/化学，实现的尺度也不一样，微观/宏观。一孔之见。

对于电磁学，我们讨巧在，我们的研究都是基于电尺寸，所以在低频，如微波段，可以轻易地人造结构，实现许多以前从来没有的物理特性。/::P

宁东大 晓星

我感觉meta所指对象，在物理上现在还是比较清楚的，模糊的是中文名词，这种模糊目前可能会有一些好处吧，

作为吃电磁饭的一员，理解现在模糊的合理性，将来如果想换名，建议称为麦特，麦克斯韦加上奇特，音译加意译

二零二零年三月五日

IEEE Transportation on Antennns and Propagation Issue 3 2020是关于 EM metamaterials /metasurface的专刊。包括综述，一共六十七篇文章。可能因为三位guest editor都是理论背景，此刊物理气味浓厚。多回顾综述为主应该是已经淡出物理层面上理论研究了（进入拓扑时代？），而进入技术发展和应用的快车道。国内有世界上最大的天线创业支持，一定会大有作为（这点已经证明了和正在进一步证明中）。

如果我没有记错，这是二零零九年在南京参加东南大学崔铁军教授的111项目的会议。那年也是近代metamaterials研究工作开始了十年。在观察了这个领域的理论研究十年后，也是那年，我被研究院“强迫”开始工程应用的研发工作。记得，在参加这个会议，应铁军邀请做了发言。但是，那时候，我没有找到感觉，只有对metamaterials概念与工程应用之间gap的思考。所以，我的主题是：I have no solution but questions to metamaterials based antennae 。经过十年不懈的努力，我想，我们找到了感觉并且开始有解了。

这是一个非常好的从全新的物理概念出发，发展出各种创新的工程技术，最终用这些工程技术解决实际挑战，通过产品实现了技术落地。

十年，在研究生涯中也就是一个不长不短的窗口。抓住了，就是机会，就是一段愉快精彩纷呈的旅程。

和所有新概念的经历一样，当metamaterials概念刚开始进入工程界视野时，甚至十多年后，一直以来都受到工程研究人员的许多诘问，怀疑和否定。其中，许多说法不无道理。但是，我一直都抱着质疑包容的态度试图理解和体会它对工程应用的潜在影响。作为一个工程师，我的纯物理概念没有那么好，所以避免对物理概念的争论一向都是关心不参与。也不论如何定义什么是，关键看，那些概念对应的工程指标是什么，有什么解决问题的新思路新方案。典型的实用主义思维方式。实践证明，it works。尽管想法做法有点“土”，但应该也算是“士”的风格，行动更重要。

最新新闻

南京大学冯一军教授来自芬兰MetamaterialsCongress 2018的现场直播:

Metamaterials Congress 2018有专场“纪念苏联科学家Veselago院士发现负折射现象里程碑论文发表五十周年。当年为超材料研究做出突出贡献的几位大牛纷纷介绍了他们和超材料不得不说的故事（some negative, some positive）。”

据他说，David Smith在历史回顾中十分谦虚，尽管他的工作也是有目共睹的，但一直在赞赏他人的贡献，如Veselago院士 Pendry 和他导师Schultz。

下面是冯教授现场拍得照片。

（作者注:真正的大家自带光环。学术成就和人格魅力。反观自己贴金的做法真的无语了。）

Smith在照片的左下角

Pentry组的论文。他们团队主要贡献应该是负折射率的实现与superlens（冯教授语）

“metamaterial”的起源

news :

metamatetial-based frequency-adaptive analog beamforming auto radar antenna.

https://www.eetimes.com/document.asp?doc_id=1332443&page_number=2

Metawave’s Metamaterial Frequency-Adaptive Steering Technology (Photo: Metawave)

frequency-adaptive auto radar antenna.

https://www.eetimes.com/document.asp?doc_id=1332443&page_number=2

Latest News: Metamaterial Market 2017-2025

“Increasing interest on developing tunable and re-configurable artificial electromagnetic materials is the key factor contributes the growth of global metamaterials market. Metamaterials are artificially structured materials used to control and manipulate sound, light, and other physical phenomena. Typically, metamaterials include several classes of electromagnetic composites including negative index materials, photonic crystals, zero index materials, low index materials and chiral metamaterials.”

http://www.lanews.org/key-factors-to-fuel-growth-of-the-metamaterials-market-through-2017-2025/

二零一六年三月二十九日

The concept of "metamaterials" has become the hottest topic, not one of, in EM thoery and engineering. Like all new topics, there have been many debates in the community since it was reported again as an engineering design in 2000.

After years, I realized that not all people have really studied the definition of metamaterials carefully and known the original idea to propose this concept.

Here, let us go thru some of the topics relevant to metamatetials from an engineering point of view as a fun.

Wikipedia

https://en.m.wikipedia.org/wiki/Metamaterial

Negative-index metamaterial array configuration, which was constructed of copper split-ring resonators and wires mounted on interlocking sheets of fiberglass circuit board. The total array consists of 3 by 20×20 unit cells with overall dimensions of 10 mm × 100 mm × 100 mm (0.39 in × 3.94 in × 3.94 in)

Metamaterials (from the Greek word "meta-",μετά- meaning "beyond") are materials engineered to have properties that have not yet been found in nature. They are made from assemblies of multiple elements fashioned from composite materials such as metals or plastics. The materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence.

Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures. Their preciseshape, geometry, size, orientation and arrangement gives them their smart properties capable of manipulating electromagnetic waves: by blocking, absorbing, enhancing, bending waves, to achieve benefits that go beyond what is possible with conventional materials.

Remarks:

three key components of metamaterials
1 conventional natural materials
2 structures arranged in some way
3 unusual EM properties

Natural atoms at optical bands and Artificial atoms at microwave bands

J Pendry:
Metamatetials and Control of Electromagnetic Fields

I think, I should include one more figure to remind the people who are still arguing the concept of metamaterials, especially, from the fields of microwave engineering. The essential idea of metamaterials is to artificially engineer the atoms with physically larger but electrically smaller size at microwavd bands similar to that of natural atoms at optical bands. In other words, we are artificially fabricating materials which have artificial atoms and feature the unique EM properties.

Sir John Brian Pendry

Sir John Brian Pendry (born 4 July 1943) is an British theoretical physicist, known for his research into refractive indices and creation of the first practical "Invisibility Cloak". He is a professor of theoretical solid state physics at Imperial College London where he was head of the department of physics (1998–2001) and principal of the faculty of physical sciences (2001–2002). He is an honorary fellow ofDowning College, Cambridge, (where he was an undergraduate) and an IEEE Fellow.

John Pendry: I knew that Russian engineer Victor Veselago had theorized a lens made out of material with a negative refractive index. In 1999 I checked whether such a lens could be perfect, expecting the usual answer—that it wasn't perfect. I didn't get it; the theory said it was perfect. I was astonished, and so was everybody else. The mechanism of a perfect lens is very strange. I still get letters saying that it is all rubbish, but this has died down.

The concept of metamaterials opened up the field. A metamaterial is a material whose electric and magnetic properties are determined as much by its structure as by its chemical composition, although the structure must be on a scale much smaller than the wavelength of light you're using.

metamaterial-based superlens

The real kick-start came when I got together with a team in San Diego who made the first material that had a negative refractive index, which was something of a Holy Grail for electromagnetism. It had been talked about for many, many years but you just couldn't find any stuff that did that.

Humor Professor

Reporter: Will metamaterials win a Nobel Prize?
JP: All I can say is that I hope they will. It is a lottery, isn't it really?

reporter: If you met J. K. Rowling, what would you say?
John Pemdry: I'd be in awe. I'd let her speak first, like the Queen.

Simple ideas have flourished as a whole new field of research looks to capitalise on "invisibility"

Pendry first gained notoriety outside the field of physics when he published an idea for an "invisibility cloak" in 2006.

The concept made use of metamaterials - whose properties are not defined by their chemical makeup but rather by their structure on the tiniest scales - to guide light around an object, rendering it in effect invisible.

An early metamaterial using repeating elements of copper split-rings and copper wires by D. R. Smith et al.

David R. Smith is an American physicistand professor of electrical and computer engineering at Duke University in North Carolina. Smith's research es on electromagneticmetamaterials, or materials with a negative index of refraction.

An early metamaterial using repeating elements of copper split-rings and copper wires. Credit: D. R. Smith et al.

David R. Smith's group in 2000 first created a metamaterial using copper split-rings on circuit boards and lengths of copper wires as repeating elements. The size and shape of the split-rings and copper posts determines what frequency of light the metamaterial is tuned to. The combination of these components interacts with the incident light, creating a region with an fully engineered effective index of refraction.

Remark:

A great work to translate the magic physical concept to a prototype experiementally.

George Eleftheriades designed the frst three-dimemensional negative-index superlens using transmission-line metamaterials.

Discussions

关于metamaterial的争论很多。一方面，大多数像我们一样做工程的，不太明白如何把那些吹得神乎其神的物理概念与工程设计相结合; 另一方面，个别老鼠屎信口呲黄，诓国家骗百姓，污名metamaterial。

在过去几年，我在许多大会报告中都试图还metamaterial个清白，也试图用工程的语言去bridge metamaterial的物理概念与工程技术。我称这个是:Translational Metamaterial Research。

我的口号是:
破除迷信，解放思想; 踏实求是，大干快上!

I will address this point three times (重要的事说三遍):
2nd:
Metamaterials are structures constructed by conventional materials for unique EM properties which have never been found in nature.

3rd:
电磁超越材料是由普通电磁材料构成的结构以实现独特的自然界还没有发现的电磁性质。

Remarks

Potential Applications of Metamatrials.

in short, the concept can be applied in any areas related to fields or waves, in particular, Electromagnetic Waves.

There is no limitation of frequency when applying the concept.

However, it should be noted that double-negative materials are considered as Metamaterials but metamaterials are absolutely NOT limited to Double Negative Materials.

However, we must break the bottleneck of performance of metamaterials, narrow operating bandwidth, high ohmic loss and complicated structures if we are going to apply them in practical systems.

For instance, besides the materials or structures falling into negative permittivity or/and permeability, the structures with zero and less than unit permittivity and /or permeability have never found in nature. Even we have found any structures in nature which feature very high permittivity and /or permeability by using the natural materials like conventional dielectric substrate as shown in the slide.

Based on my rethinking, we have developed many technologies for Antennas, absorbers, and transmission lines, including

1 ultra- low profile antennas for cellular base-stations, RFID readers, and radar systems;
2 electrically larger zero-phase shift loop antennas and arrays for UHF RFID reader and for WiFi;
3 ultra-thin planar lens for 5G massive MIMO base stations;
4 ultra-thin wideband magnetic absorbers;
5 high-gain Vivaldi antennas and patch antennas;
6 ultra-thin FP cavity antennas;
7 utral directional MRI coils;
8 consistent-gain, wide-angle composite right/left handed leaky wave antenna;
9 wide-band low-profile CP antennas
10 ultra-small UHF antennas for small cells
11 spoof surface plasmon-fed dielectric resonator antennas with missing mode;
12 spoof surface plasmon transmission lines

Recent topics

A True Metasurface Antenna

Mohamed El Badawe, Thamer S. Almoneef & Omar M. Ramahi

Scientific Reports 6, Article number: 19268 (2016) doi:10.1038/srep19268

Published online:13 January 2016

Abstract

We present a true metasurface antenna based on electrically-small resonators. The resonators are placed on a flat surface and connected to one feed point using corporate feed. Unlike conventional array antennas where the distance between adjacent antennas is half wavelength to reduce mutual coupling between adjacent antennas, here the distance between the radiating elements is electrically very small to affect good impedance matching of each resonator to its feed. A metasurface antenna measuring 1.2λ × 1.2λ and designed to operate at 3 GHz achieved a gain of 12 dBi. A prototype was fabricated and tested showing good agreement between numerical simulations and experimental results. Through numerical simulation, we show that the metasurface antenna has the ability to provide beam steering by phasing all the resonators appropriately.

narrow band impedance matching and high insertion loss?

11.7dBi realized gain without information about crosspol levels

symmetric radiation pattern

据南大的冯一军通告:::

2016年11月19日-20日，国家自然科学基金委员会（以下简称基金委）第169期双清论坛在北京召开。论坛主题为“超构材料中功能基元的设计、制备及新奇性能”。会上大家认为: 超构材料是通过人工功能基元的设计和空间序构的排列来构筑的新材料，它展现出许多新奇的、超常的力、热、光、声、电、磁等物理特性。
会议取得了以下重要成果：阐述了“超构材料”的概念和内涵，定义了超构材料基于功能基元设计和空间序构的材料研究范式；展望了“超构材料”这一新概念对基础研究、应用研究、颠覆性技术突破的前景；初步凝练了关于“超构材料”的多种功能材料融合的关键性技术，以及多物理场耦合和跨尺度界面物理衍生现象的重大科学问题和跨尺度逆向设计、可控制备、动态调控等关键性技术问题；凝聚了一批材料、物理、信息、化学、生物医学等高学科交叉背景的优秀研究队伍。

Geometric phase coded metasurface: from polarization dependent directive electromagnetic wave scattering to diffusion-like scattering
Ke Chen, Yijun Feng, Zhongjie Yang, Li Cui, Junming Zhao, Bo Zhu & Tian Jiang
Scientific Reports 6, Article number: 35968 (2016)doi:10.1038/srep35968

Electrical and electronic engineering Metamaterials

Ultrathin metasurface compromising various sub-wavelength meta-particles offers promising advantages in controlling electromagnetic wave by spatially manipulating the wavefront characteristics across the interface. The recently proposed digital coding metasurface could even simplify the design and optimization procedures due to the digitalization of the meta-particle geometry. However, current attempts to implement the digital metasurface still utilize several structural meta-particles to obtain certain electromagnetic responses, and requiring time-consuming optimization especially in multi-bits coding designs. In this regard, we present herein utilizing geometric phase basedsingle structured meta-particle with various orientations to achieve either 1-bit or multi-bits digital metasurface. Particular electromagnetic wave scattering patterns dependent on the incident polarizations can be tailored by the encoded metasurfaces with regular sequences. On the contrast, polarization insensitive diffusion-like scattering can also been successfully achieved by digital metasurface encoded with randomly distributed coding sequences leading to substantial suppression of backward scattering in a broadband microwave frequency. The proposed digital metasurfaces provide simple designs and reveal new opportunities for controlling electromagnetic wave scattering with or without polarization dependence.

(a) Distinct directive EM wave scattering dependent on the incident polarization by metasurface with regular coding sequence. (b) Polarization insensitive diffusion-like reflection by metasurface with randomized coding sequence. (c) Details of the corrugated meander line structured unit cell which is oriented at the rotation angle of α = 90° with respect to x-axis. The violet arrow represents the orientation of top metallic pattern. The optimized geometric configuration of the unit cell is by, in millimeter, p = 8, h = 2, a = 4.6, b = 4.25, and w = 0.25.

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Investigation of mechanism: spoof SPPs on periodically textured metal surface with pyramidal grooves
by Lili Tian, Jianlong Liu, Shutian Liu

Scientific Reports 6, Article number: 32008 (2016)

In microwave and terahertz frequency band, a textured metal surface can support spoof surface plasmon polaritons (SSPPs). In this paper, we explore a SSPPs waveguide composed of a metal block with pyramidal grooves. Under the deep subwavelength condition, theoretical formulas for calculation of dispersion relations are derived based on the modal expansion method (MEM). Using the obtained formulas, a general analysis is given about the properties of the SSPPs in the waveguides with upright and downward pyramidal grooves. It is demonstrated that the SSPPs waveguides with upright pyramidal grooves give better field-confinement. Numerical simulations are used to check the theoretical analysis and show good agreement with the analytical results. In addition, the group velocity of the SSPPs propagating along the waveguide is explored and two structures are designed to show how to trap the SSPPs on the metal surface. The calculation methodology provided in this paper can also be used to deal with the SSPPs waveguides with irregular grooves.

A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three-dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the laser beam. In recent years, it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multilayer metamaterial holograms. A background free image is formed at a new frequency—the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analysed and prospects for future device applications are discussed.

Here’s a new invention that, while potentially useful, is even more interesting as an illustration of the nature of sound: the acoustic prism. When light enters a prism made of some refractive material, the sub-components of that light have their paths affected slightly differently, based on their wavelength (color); the result is that the combined white-looking light is split apart so its various component wavelengths (colors) are visible. Now, researchers have created a similar device for sound, which passively and naturally splits sounds into their component frequencies.

This prism device is actually a sort of “leaky wave” antenna, a term coined in the context of electromagnetic waves. In both cases, a meta-wave that is a complex mixture of componentwaves is split into those components as the physical properties of each leads it to escape at different points along the length of the antenna. This acoustic device is no different — it has a long tube with periodically placed points at which different sound frequencies can escape. As it moves down the tube, sounds hit specialized double-chambers separated, each split by a membrane that vibrates and delays the release of the sound depending on its frequency. When this delayed sound then exits the tube, the effect over the entire prism is a splitting of the overall sound into different frequencies.

ET
An ‘acoustic prism’ can split sound the way a regular prism splits lightBy Graham Templeton on August 10, 2016

(a) Snapology is a type of modular, unit-based origami in which paper ribbons are folded, and ‘snapped’ together to assemble extruded polyhedra, such as the extruded icosahedron shown. (b) Some of the geometries that can be made in this way, including the extruded icosahedron, are almost rigid. (c) In contrast, other geometries, including the extruded cube, have multiple degrees of freedom and can be easily deformed.

Selections of beautiful photos of metamatetial-based designs

朋友议论

京 张生俊
@bigbug848180 metamaterials本来就是过去周期结构，光栅，频选，光子晶体等这类研究的延伸版，天才的veselago从数学完美性提出，天才的pendry提出一种变换光学设想，加上现在计算技术的发展，才能够深入起来。但pendry的基础是单元的谐振，意味着很窄的频带，所以是有局限性的，当前一些新概念宽带实现提法实际上相当于人工等效粗糙表面。

@bigbug848180 metamaterials并不那么神，而是被神话了。现在把其外延加宽了，有人把频选光子晶体都称为metamaterials，无可厚非，但是不同角度。metamaterials当初有4个定义，都是从不同角度看问题给出的。

我:
@张生俊(航天14所) 有道理，但不是这么直接简单。我不是很清楚光栅，频选或光子晶体是否涉及到一个在材料特性概念上的延展，比如等效介电常数小于一甚至为零，为负的概念。其实我觉得，至少是对我做天线的，最重要的是概念突破，而具体做法是次要的，我们已经有很多手段了。一孔之见。/:@)

京 张生俊

@陈志宁-新国大 负折射是从材料角度研究，而光栅，频选是从结构功能形式角度研究。就像硅，从材料角度是三族的一种导电材料，从物理角度，是一种可掺杂半导体，从光学角度，是有禁带的电子晶体。折射率为负这件事的争议是否结束？当时munk认为science上的实验结果是高次模所致，我没深研究，对此不确认。我觉得其实不在于创造几个万能新概念，而在于将其性能利用起来。比如天线，天线辐射与地，与大地等等条件及其影响，至今似乎还有很多需要研究解决的。再比如，磁单极，需要一个天才来发展。管窥之见，请批评。

@陈志宁-新国大 当年50年代模拟等离子体时就发现传输截止不能传播的问题，只是大多数人没有去想负折射的事，没去想负参数的事，只有veselago去想了。

我:

@张生俊(航天14所) 对我一个天线工程设计的人，我从来关心但无法参与物理概念的讨论。我的做法是充分理解并利用物理界的新概念，使之工程化，并解决实际问题是主要使命。所以我基本不用折射率的说法而是s参数，等效e和u, 色散等帮助理解。我的另外一篇美篇介绍了我利用其概念在天线设计上的成功案例。当然，一些产品化的工作暂时无法分享。我总是认为metamaterial如同它的名字，是一个广范的概念，至于已有的结构是它的子集，正如，在有人这个概念前，可能有了男人女人，甚至更早的，只有一个个具体的人的概念一样。所以，如你所述，具体是什么名字其实是角度问题和概念的层次问题。对我们工程设计创新而言，更高层次上概念创新是根本的，绝对超出具体技术的创新。比如，在我真正意识到metamaterial概念的精髓前，传统设计天线的套路越走越窄。我几近放弃天线研究，转去系统设计或信号处理。各见，仅供参考，但不欢迎批判/::P

安 商锋

精辟精辟

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Beautiful EM is waving in the light
Magic Metamatrials are flying in sky
Curious Explorers are traveling at night
Talented Engineers are working on artworks