WECS, Laguna Beach, and Meeting John Pendry
David Vier, Willie, Syrus and I completed the poster maybe a day before the
Workshop on Electromagnetic Crystal Structures (WECS) in Laguna Beach that
Eli Yablonovitch had invited me to. From the agenda, I saw that John Pendry
was going to be there, and I was really interested to see what he would think
about our approach to the wire medium. Shelly, who was also going up to the
meeting, suggested we meet with John together, so we agreed on a time to meet
at the poster session.
It was the first time I'd ever met John; he was incredibly good natured and
extremely approachable. He graciously agreed to look over our poster, and
after just a few minutes confirmed that we had an equivalent way of arriving
at a microwave plasmonic medium. He was actually amused by the loop-wires
that we had made.
"Who made all of those loops?" John wondered.
"Syrus and Willie, a couple of graduate students in our lab."
"Oh dear!" John kind of laughed. "Seems like a lot of work. I think I'll
stick with my thin wires, thank you very much," he added, jokingly.
Thin wires, loop wires, it didn't matter to me; we had done it! We now had a
plasmonic medium that was easy for us to make and measure, and which also had
John Pendry's endorsement. I was completely satisfied.
"By the way, are you coming to my talk?" John asked. "I think you’ll find it
very interesting as well."
Shelly and I, of course, attended all the talks at the meeting, and John's
talk was top on our list. And the timing could not have been better: John was
about to give his first talk on the split-ring medium.
WECS，Laguna海灘，與John Pendry見面
可能是Eli Yablonovitch邀請我在Laguna海灘舉辦的電磁晶體結構研討會
Workshop on Electromagnetic Crystal Structures（WECS）的前一天，David Vier,
Willie, Syrus和我完成了海報。從會議議程中，看到John Pendry也即將參加，我真的
很感興趣看他會怎樣看待我們處裡導線介質的方式。Shelly也北上參加這個會議，他建議
我們與John見面，所以我們約定了一個時間在海報會議上見面。這是我第一次見過John;
他是非常善良且極為平易近人。他欣然地同意看看我們的海報，並且在短短的幾分鐘後確
認我們用相同的方法得到微波電漿介質的。他實際上也是假設迴路和線圈的方式跟我們所
做的一樣。
“誰做的所有這些迴路的？” John好奇地問。
“Syrus and Willie，我們實驗室的一對的研究生。”
“哦，天啊！”John式的笑了起來。“似乎是一個大量的工作，我想我會堅持我的細導
線，非常感謝你，”他開玩笑地補充說，。
這些細導線，電線圈，對我並不重要; 我們已經做到了！我們現在有對我們來說容易製造
和測量的電漿介質，並且也有John Pendry的認可。我完全滿意。
“順便說一下，你能來我談談嗎？” John問。“我想你將也會覺得非常有趣的。”
當然，Shelly和我，在所有參加會談的會議上，能和John的談話是我們名單上第一名。
時間點再也不可能更好了：John正要給裂環介質上的第一次演講。
I had started playing around with the wire medium to create something that
would have a negative ? at microwave frequencies, with a goal of emulating
the nanoparticles we were working with in our microscopy experiments. I had
not thought beyond that possibility.
But John's talk changed that. He was now interested in trying to create
artificial magnetism, and proposed a series of new structures, from
conductors rolled up into little tubes like "Swiss rolls," to little, flat,
rings with gaps in them, he called "split-ring resonators." Though there were
no inherently magnetic materials in these structures - they were pure
conductors - John predicted they would have a magnetic resonance, with a
regions where the effective permeability, μ could be controlled, with large
positive values or even negative values.
我已經開始玩弄在微波頻率波段的光與導線介質所產生的東西，會產生負的？目標是
模擬我們在顯微鏡下工作與奈米粒子。我還沒有想過超越這種可能性。
但John的談話改變這一切。他現在有興趣製造人工磁性，並提出了一系列新的結構，
從導線捲成如“瑞士卷”，以小，扁平，環中有縫隙，他所謂的“裂環共振器“。雖然在
這些結構沒有本質上的磁性材料- 他們是純粹的導體 - John預言他們將有磁共振，與那裡
區域的有效磁導率μ可以被控制，以大正值或甚至負值出現。
"A negative μ?! That's impossible! What does that even mean?" Shelly, who
was sitting next to me during John's talk, was leaning over with a shocked
look on his face. "John's crazy! There's no such thing as negative μ. I've
never heard of it."
I thought about it. We all accepted that ? could be negative. Why should a
negative μ be impossible? What was really exciting was the fact that John
was now proposing an artificial magnetic structure that could control μ.
With the wires, that could control ?, and the rings that could control μ,
you could create materials with completely arbitrary electromagnetic
properties. That's what was really amazing.
“負μ？！那是不可能的！這是什麼意思啊？” 在John的談話中，Shelly就坐在我旁
邊，俯身並在他的臉上用震驚的表情。“John太瘋狂了！我從來沒有聽說過有這樣作為
負μ的東西。”
I thought about it. We all accepted that ? could be negative. Why should a
negative μ be impossible? What was really exciting was the fact that John
was now proposing an artificial magnetic structure that could control μ.
With the wires, that could control ?, and the rings that could control μ,
you could create materials with completely arbitrary electromagnetic
properties. That's what was really amazing.
I returned to UCSD, fired up about demonstrating artificial magnetism. Shelly
was also now somewhat interested, because he had believed that a negative μ
was impossible, and was curious to see if this impossible material could be
made. So, we were both motivated in our own ways to continue building
microwave structures, at least for a little while longer.
Also, I'm pretty sure, Shelly and I were the only ones interested in building
the artifici al magnetic structures at that point.
我想過這個問題。我們都接受了？可能是負的。為什麼負μ應該是不可能的？真正令
人興奮的事實是John現在正建議一個可以控制μ的人工磁結構。與導線一樣可以控制負的
介電常數ε？而且可控制μ的環，你可以創造完全任意電磁特性的材料。這是非常令人驚
奇的。
我回到了加州大學聖地亞哥分校，啟動了演示人工磁性。Shelly是現在也有點興趣，
因為他認為一個負μ的磁導率是不可能的，並且很好奇想看看這個不可能的材料被製造出
來。
所以，至少有一段時間我們是出於自己的方式來繼續建造微波結構，。
另外，Shelly和我唯一的興趣是建造人工磁結構。這一點我相當的肯定。
You see, the WECS was a conference about photonic crystals. And, the vast
majority of people working on photonic crystals are, naturally, interested in
photonics, which usually is about visible light or light at near-infrared
wavelengths. Probably ninety-nine percent of the people at the workshop had
no interest in microwaves. When it came time for questions, there was an
uncomfortable silence, except for one person. That person was George Merkel,
a researcher from the Army Research Laboratory.
George came across as a little annoyed. "Everything you're talking about has
been done before," George announced. "These ring structures, the wire
structures - they were all looked at in the 40s and 50s, mostly by Army
researchers. It's interesting stuff, but it didn't go anywhere. There was
some thought of using the wire medium as a way to model wave propagation in
the Ionsphere, but it didn't catch on. Some people made lenses and other
quasi-optical devices."
你看，Workshop on Electromagnetic Crystal Structures (WECS)是一個關於光子
晶體的學術會議。而且，絕大多數的人們的工作的主要都是光子晶體，自然地，感興趣的
是光子，通常大約是可見光或是在近紅外線波長的光。也許在研討會上99％的人對微波毫
無興趣。當來到問問題的時間，有一種令人不舒服的沉默，除了一個人。
那人是George Merkel，一個來自美國陸軍研究實驗室的研究員。George看起來有點
惱火。“你說的每一件事在之前早已經做過了，” George公佈。
“這些環狀結構，導線結構 –大多是被陸軍研究人員，它們在1940年代和1950年代都
曾看過了。這是很有趣的東西，但它並沒有任何用途。利用導線介質有些被思考做為在電
離層波傳播的模型一種方式，但它並沒有流行開來。有些人做鏡頭和其他準光學元件。“
It turned out that George Merkel was right! He forwarded a big stack of old
papers to Eli, who didn't have time to read them all and who then sent them
on to me. The wire medium had indeed been discovered by Rotman, and the
split-ring resonator as a magnetic material had been described by
Scheulnekoff. In fact, their approach was an engineering one that was much
closer to the way I was now thinking about these things.
One of the difficulties of all of those papers, though, was that the
effective medium theories were rough and approximate, having been done before
there were full-wave numerical simulators that would be able to give precise
results. The formulas, even if approximate, were difficult to derive and
cumbersome, sometimes expressed as infinite sums that would have to be
truncated. Every time you would change the geometry, even a little, you might
need to derive entirely different formulas. It was daunting! I could see how
difficult it might have been to arrive at a well-designed artificial
electromagnetic material using the approximate analytical formulas that gave
the only viable design path at the time.
John Pendry's work, while an independent rediscovery of sorts, had cast
artificial materials in a new light. It was the perspective of a physicist
rather than an engineer, and that opened up new opportunities.
原來，George Merkel是對的！他轉發的一大堆舊論文一大疊給Eli，他沒有時間閱讀
所有這些論文，然後Eli把它們寄到我這裡。Rotman確實已經發現導線介質，並且做為磁
性材料的裂環共振器的已經被Scheulnekoff描述。其實上，他們是一個工程的方法，這就
更接近我現在對這些事情的想法。
One of the difficulties of all of those papers, though, was that the
effective medium theories were rough and approximate, having been done before
there were full-wave numerical simulators that would be able to give precise
results. The formulas, even if approximate, were difficult to derive and
cumbersome, sometimes expressed as infinite sums that would have to be
truncated. Every time you would change the geometry, even a little, you might
need to derive entirely different formulas. It was daunting! I could see how
difficult it might have been to arrive at a well-designed artificial
electromagnetic material using the approximate analytical formulas that gave
the only viable design path at the time.
John Pendry's work, while an independent rediscovery of sorts, had cast
artificial materials in a new light. It was the perspective of a physicist
rather than an engineer, and that opened up new opportunities.
然而，所有這些論文其中之一的困難是有效介質理論是粗糙的和近似的，之前就已經
有全波數值模擬器能夠提供精確的結果。這些公式，即使是用近似，也是難以推導和繁
瑣，有時候表示為無窮求和將必須被截斷。每一次你會改變的幾何形狀，即使是一點點，
你可能需要推導完全不同的公式。它是令人望而生畏的！我能看到這些有多麼困難它可能
到達一個精心設計的人工電磁材料採用近似解析的公式給出了設計時的唯一可行的路徑。
John Pendry的工作，當他各式各樣的獨立重新發現，已經給人工材料一種新的觀點，這
是從物理學家的角度而不是從工程師的角度來看，這開闢了新的機會。