This is Duke University.
I think the first thing to say is why aren't all lenses perfect and the reason for that
is that when you use an ordinary lens it essentially writes the image using the light it's given,
but it's as if the light was a broad pencil and that pencil has the width essentially
of the wavelength of light. With ordinary technology, you can't squash light into anything
smaller than a wavelength, but if you stare at the equations governing the way light moves
long enough, you can realize that that doesn't have to be the case. There is a way of making
light even smaller, but you really have to have some very special things happen. Otherwise
people would have discovered that long ago and they haven't. Everybody's been stuck with
this limit to the resolution of lens. By the way, that's very limiting because with an
ordinary microscope you can see the living cell, but you can't see inside it and people
really need to do that so the resolution is a big issue.
You have to do something which never happens in nature. There are no materials which do
this in nature-- and that is you have to have a material which, when light enters it, it
bends the wrong way. Our contribution, jointly with David, was first of all, I developed
some new materials called metamaterials where instead of just readjusting a chemistry of
a material we also looked at the internal nanostructure so that you, as well as tuning the chemistry,
you have this additional thing you could do which would change the properties and it turns
out that one of the properties you can alter is which way the material bends light and
you can realize its negative refracting property like that.
It was thanks to Physical Review Letters for rejecting our paper immediately that allowed
us to then go and do a literature search and actually find Veselago's paper.
Veselago was the first one to point out the importance of negative refraction and he investigated
theoretically many of the things which you can achieve with that. But there's one thing
he missed, which is kind of strange because he's so smart and he did see so many things,
and it was this question you ask of the perfect lens. And he realized that a negative refracting
material could make a lens and he even has a, I think he has a picture in his paper of
it focusing light, but what he didn't get to was that that focus is perfect because,
like nearly everybody else, and like myself, actually, everybody assumed that the focus
had to be limited by the wavelength of light and it was only that I saw there was-- you
know if you see the smallest chink of an anomaly in science, you shouldn't let it pass. You
should pick away at it until you understand what it is and I saw a little small chink
of an argument-- it wasn't a very good argument-- as to why this lens shouldn't be limited in
this way.
And so that persuaded me to sit down... I was head of our department at that time so
I had very little time for my research so it was Sunday... and I had a little time before
dinner. It wasn't a hard calculation. I calculated how perfect was this focus, and nobody bothered
to do that before. I came out with the answer: no limit. It could focus anything. And I thought
this has got to be wrong and if I publish this I'm going to be condemned as someone
not worthy of being a scientist or something. And indeed I was, but it didn't turn out to
be wrong.
No one knew anything about Veselago. We just, so Sir John suggested, had been thinking about
artificial materials and basic science-- it would be interesting to fiddle with the properties
of materials for various reasons and he had proposed something called split ring resonators
which had this magnetic response-- artificial magnetic response-- and our group in San Diego,
just for fun-- this was nothing that anyone would have funded and probably very few people
would have published it-- just for fun we wanted to demonstrate the properties of this
to see if it was true. And so we did that and it was just to show that yes these rings
are magnetic, nothing about negative index or Veselago or anything and that's the work
that we wrote up and submitted to Physical Review Letters and they instantly with a form
letter came back and said this does not appear to be important enough to even send it out
for review. We still thought that it was interesting and so that's the point which I sat down and
said I'm going to see if anyone else has ever looked at a material like this with a negative
epsilon and a negative mu, and the one paper popped up-- Victor Veselago from 1967 or 68
and so that paper was-- if this could ever be realized, you'd have all these crazy physics
effects, you'd turn light backwards, you'd change the Doppler shift, you'd change Cherencov
radiation, you'd change Snell's law. It was really a fundamental paradigm shift and when
he wrote that paper he was-- the Russian schools were very tough, the Russian sort of thinking--
and he took a lot of flack for having written something so unrealistic and unachievable
and a lot of people told him he just did it to get a paper. So when our experiment was
published, he was so happy with it.
It was at a meeting in Laguna Beach. Was it PECS1 or PECS2?
I think that was PECS1. It was called WECS then.
And I gave a talk on my metamaterials. They weren't called metamaterials then and I got
two examples. One was which made the electrical response negative and one which made the magnetic
response negative. The second one is the now famous split ring structure and David and
Shelly were in the audience and I don't know if it's true but somebody said Shelly fell
off his chair.
Yeah he was sitting next to me. Shelly Shultz was my advisor at the time.
And so David came up after my talk and said hey could we make this stuff. Be my guest,
so I was delighted at that and the rest is history as they say.
I tend to miss why things are so controversial. When I saw the-- when John sent me the paper,
it just made perfect sense to me so I probably didn't give enough feedback because I didn't
see anything wrong with it and a lot of the things that have come up I was just blindsided
by the fact that they were controversial. And a lot of the, I think, a lot of what made
things controversial is people adhere to sort of undergraduate level arguments which are
designed to give you a good understanding, but not a perfect understanding. When things
get more complicated you have to remember to drop those simple things and so I have
a bad memory anyway. I don't remember those simple things. I always start from scratch.
And I think that's the way John works too.
We had been looking at obviously the negative refraction had raised lots of controversy
and then the controversy was settling down and people were really trying to demonstrate
the perfect lens which happened in 2005 at optical wavelengths and moving along on that.
Around that time or parallel, I started looking at anasyntropic materials which are materials
that aren't the same in every direction, and realizing that there was a lot of freedom
there. So much freedom that we didn't even have design tools to actually take advantage
of all that. And it was some conversations I was having with John saying you know we
need some kind of tool that can help us make sense of all this or give us a clear path.
And John should describe this himself, but he went back to something that he had done
in 1996 just as a computational tool and said why don't we dust this off and use this as
an actual design tool and that approach is now called transformation optics. That was
what emerged from our discussions and somewhere along the way John decided hey, we can make
an invisibility cloak out of this. Even partially as a joke I think, but the math held up and
you could write down the prescription for a cloak and it was fairly simple. I wasn't
actually in the room when John presented this idea.
Yes it was a meeting in San Antonio, right? And my-- what was that lady called? Valerie
Browning. And Val wrote to me and said we'd like you to come to this meeting and try to
be controversial. So ok I thought. I'll make them laugh rather than be controversial. So
I told them about some of the metamaterial ideas and so on and the end I really didn't
think more of it at the time other than it was something which was amusing. And I said
by the way we could make something invisible and I just gave a sketch and one slide with
a formula on it and I sat down and I expect everybody to laugh. Straight faces. Val came
up to me afterwards and offered me quite a lot of money to make this thing which I--
some of which I took, but not all of it. And David wasn't there. You were ill with a cold
I think. But Dave Scherick and Jack was there.
From our lab were there.
Yeah. And they reported back home and pretty soon the phone lines were hot and David said
we've got to build this stuff. Great. So we said let's take it seriously. We wrote the
theory paper and that came out pretty fast. And then you built it.
Well what happened was we wrote the theory paper and it went into Science and normally
you write a paper and there might be some interest but you know it doesn't knock you
out and it doesn't change your life, but the response to this-- the idea that you could
make an invisibility cloak-- was so ridiculous in terms of not just hitting the scientific
press, but hitting the popular press, and our lab started getting reporters-- they weren't
even happy with a phone interview. They wanted to come here and when I'd say it's just a
theory paper, they wouldn't believe us. They'd start looking around the lab as if we had
some big clandestine program going on and speculation was kind of growing rampant and
so we had plans to build this thing and we decided we better build it really really quickly
and take whatever shortcut we could do to really show people where it's at and we'll
calm everything down.
No no no.
So we start working and you know the exact prescription was a little too tough to handle
but we made a couple compromises and we were able to do the experiment. We did it within
four months, start to finish. And so we did that. Again submitted it to Science and they
were very eager to have it, and I thought ok, well it clearly shows the limitations.
It's bandwidth limited, it's lossy, it's microwaves. No one's going to care about this. This is
going to calm everyone down. And then that got published and again this turned into a
gigantic media blitz.
I think very soon. The commercialization is something that's started because we have actually
some good champions that are out west in a company called Intellectual Ventures that
actually started acquiring the intellectual property and bringing to that basic research
that we've been doing some marketing and some searching for potential applications and areas
where they can make a difference. And they have access to a lot of interesting resources
including Bill Gates who's become a big proponent of metamaterials and actually himself very
interested so with all that resource out there, they looked around and initially identified
one sector where they could create a metamaterials product which is in the area of satellite
communications. And that was spun off and formed a company which is now called Kymetta
and they're doing pretty well. Hoping to launch products this quarter.
There's one other thing I should say about exploitation and that is if you have a technology
which is really transformational it does take a long time before it gets through to practical
devices which have to be 100 percent reliable and 100 percent understood. The example I
like to quote is the laser, which you know first-- the first laser was in the 1950s and
it was known at the time as money acquisition screen for expensive research because everybody
thought it was interesting but useless. Now imagine today which is more than half a century
later all the applications of lasers that we have. We could hardly live without them.
Will I think we should be able to use some of these metamaterial concepts not necessarily
in the original formats of the perfect lens but the realization that through these materials
you can actually break this resolution limit of optics and we should be able to see things
on the nanoscale in the next ten years.
Metamaterials started in a very small way but I think now when you ask where is the
center of metamaterials actions there are many places which are doing a lot of work
and very fine work, but personally I always look to Duke as the place where the exploitation
of metamaterials is a fulcrum of what goes on in the subject, particularly as David has
been so, and his team, have been so energetic in driving forward the metamaterials. Duke
has had and will have a very important role. I always tell my students that however bright
the ideas are that you have as a theorist, and I'm a theorist, my students are theorists,
that they will not live as ideas unless somebody picks up and runs with them and makes something
useful out of that repays your debt to society for all the money and indeed the fun you've
had in developing these things and the Duke team is doing that in spades.
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