Material With Negative Refractive Index Created

holy_calamity writes "The race to build a material with a negative index of refraction for visible light has been won by researchers in Germany. The advance could lead to super-lenses able to see details finer then the wavelength of visible light, or the previously predicted invisibility cloak for visible light." From the article: "[The researcher] determined the refractive index of the material by measuring the 'phase velocity' of light as it passed through. His measurements show the structure has a negative refractive index of -0.6 for light with a wavelength of 780 nm [the far red end of the visible light spectrum]. This value drops to zero at 760 nm and 800 nm, and becomes positive at longer and shorter wavelengths."

It's good news ...

[jfclavette]

... for stalkers worldwide !

Re:Why do Germans seem ...

[anonymous22]

It's the beer.

Free University

[DerangedAlchemist]

As I understand it, post secondary education has been completely free for the past 200 years.

Re:

[SageMusings]

Not much else to do in that weather. How many days of sunshine do they get?

Re:

[antek9]

Well, more than you in your parents' basement, don't you think? ;)

Re:

[Fordiman]

It'll never happen. Respectable intellectuals hate to hear things that aren't politically correct, and as such tend not to test them.

Re:Why do Germans seem ...

[instarx]

It'll never happen. Respectable intellectuals hate to hear things that aren't politically correct, and as such tend not to test them.
Three points...
1. Not only won't it happen, it CAN'T happen. IQ tests are culturally biased. Comparing different cultures by measuring IQs has to many uncontrolled variables to provide meaningful results.

2. IQ test don't measure anyting other than ability to take IQ tests.

3. Don't make the mistake of thinking that just because something is politically incorrect it isn't also morally or ethically incorrect, or just plain vile and wrong.

Re:

[antek9]

I'll second the other reply, it will most likely never happen. On the other hand, you seem to be implying that one such study for people of German descent already exists, or why do you take for granted that their IQs are superior? Please elaborate.

Well at least the hearing defect thingy is hereditary up to even the highest political circles over there. Here, I mean.

yes, but RTFA, they were not first.

[PrinceAshitaka]

They were first to do this in the 700 nm range but the article state that previously this could only be done in the 1400 nm range. I guess 700 nm is significant because it is the start of the visual spectrum. 700 is red i think.

Re:yes, but RTFA, they were not first.

[wolfgang_spangler]

They were first to do this in the 700 nm range but the article state that previously this could only be done in the 1400 nm range. I guess 700 nm is significant because it is the start of the visual spectrum. 700 is red i think.

The article agrees with the summary. They were (according to the article) the first to do this for visible light. No claim was made that the German team has created the first ever material with a negative refractive index, just the first material with a negative refractive index for visable light.

Re:yes, but RTFA, they were not first.

[Anonymous Coward]

I actually achieved this a couple of years ago. But the phone rang and I set it down somewhere, and now I can't find it.

Re:yes, but RTFA, they were not first.

[LearnToSpell]

You can't find the phone? It's probably under your invisibility cloak. Try the pager from the base.

Re:

[cbacba]

Noting the wavelengths that it was good for indicates that the results are currently very narrow band. The question arises whether or not the phenomena can only be dealt with in a very narrow band or whether additional work can be used to expand the bandwidth substantially.

If the phenomenon can only be dealt with in narrow band, the 'invisibility' aspects are strictly BS. Other facets from the 'magic' of this could produce some significant benefits. Possibly higher powered microscopes, perhaps a method o

Visible spectrum and cones

[benhocking]

Red is ~700 nm and violet is ~400 nm. A typical human can see light from the range of 390-750 nm with the aid of three cones. The three cones are the "red" cone (optimal at 564 nm), the "green" cone (optimal at 534 nm), and the "blue" cone (optimal at 420 nm).

Re:Visible spectrum and cones

[silentounce]

Yes, the "far red end". Finally, I shall have my revenge. There shall be no more red. My fellow color-blind brethren rejoice. No longer will they laugh and point at us. That's not green! You idiot! Idiot? I think not. Our time is now.

Re:

[fm6]

It's worth mentioning that these values vary slightly from person to person.

Human vision can extend a bit further

[Viol8]

People who've had artificial lenses replace their own (because of cataracts or some other ailment) apparently can see the near ultraviolet which is said to be blueish-white. The reason for this is because the lens blocks these wavelengths but the cones are sensitive to them. Perhaps the wavelengths are blocked because they could be harmful to the retina or perhaps its just one of those biological quirks.

Also if you make the source REALLY bright then apparently human vision can extend a very short distance i

Tetrachromats need not apply

[benhocking]

Actually, it doesn't matter how many cones you have; it matters what range of frequencies they cover (for purposes of invisibility). The cones I mentioned are optimal at the points specified but cover the entire "visible" range. The only advantage a tetrachromat would have for this cloak is if their fourth cone extended the range of their visible frequencies (which it does tend to do). However, you could also have only 2 cones and still have a visible range outside of what is considered normal, so being a t

Re:

[JesseL]

Slashdot even had a previous article on it (shock!):
http://science.slashdot.org/article.pl?sid=05/04/2 5/1232218 [slashdot.org]

You may be a bit mistaken..

[Khyber]

560 nm diode laser - red spectrum (red visible dot) I think you might be mistaken, this is coming from a very very low-powered diode laser from my lighter. These have been around for YEARS, though never as cheap as they are now.

does this mean?

[jforest1]

people can wear defense cloaks to prevent the effect of the military's microwave guns (http://www.telegraph.co.uk/news/main.jhtml?xml=/n ews/2004/09/19/wirq319.xml [telegraph.co.uk])?

--josh

obligatory

[owlnation]

I, for one, welcome our new invisible overlords... wherever you are...

Re:

[MollyB]

I see these comments customized for almost every story, but I don't know what the "in-joke" is. Most of the posts are from an AC, but yours isn't. Would you (or anyone) clue me in as to the reason you find this funny? They're never modded up, so is it just schtick or what?

Re:

[Luteus]

http://en.wikipedia.org/wiki/Slashdot#Culture [wikipedia.org]

Re:obligatory

[zero_offset]

It's based upon an episode of The Simpsons.

http://en.wikipedia.org/wiki/Overlord_meme [wikipedia.org]

Re:obligatory

[Anonymous Coward]

you must be new here...

Re:

[networkBoy]

Damn near the most informative I've ever seen that post!
-nB

Re:

[Anonymous Coward]

Just didn't make the connection. Duh.

I believe you mean d'oh.

This will revolutionize...

[Anonymous Coward]

small penis jokes at physics conventions.

All right!

[morgan_greywolf]

Nothing to see here. Move along.

Re:

[It'sYerMam]

If I had been drinking coffee, I would have sprayed it on my keyboard. Not often a troll becomes funny!

Invisible to Infra-Red Heat-seekers?

[sanman2]

Well, the previous articles on cloaking concepts have talked about invisibility due to light passing around the object, like water around the pebble in the stream. So, if this negative refractive index material works on red light at the far end of the visible spectrum, then it's pretty close to infra-red range. This could then be used to mask an object from infra-red or thermal detection. So even if we're not yet invisible to the naked eye, one could make camouflage optics that mask your thermal signature f

You're So Wrong

[Aqua_boy17]

Actually I found a picture of it which I'm posting here for your benefit:









Pretty cool, huh?

Negative or less than one?

[wsanders]

So light goes backwards in this doodad?

We're always looking for ways to make light go faster than C. Customers complain about network latencies between SF and London, and we have to explain about the speed of light. Now there's an alternative to digging a fiber optic trench through the mantle of the Earth!

Re:Negative or less than one?

[HotBBQ]

We're always looking for ways to make light go faster than C.

Write it in Java.

Re:Negative or less than one?

[elzahir]

No, he said _faster_

Re:

[l2718]

So light goes backwards in this doodad?
We're always looking for ways to make light go faster than C

This is a common misunderstanding. The light will always go forward, and never at a speed exceeding the speed of light. It's true that the index of refraction will be less than 1, not negative. However, it is a function of the phase velocity – the ratio of wavelength to frequency, which is a mathematical abstraction (the speed at which peaks of the wave travel). It can exceed 'c' as demonstrated he

Re:

[imsabbel]

Actually, the index of refraction IS negative, which is the whole point.

Re:Negative or less than one?

[FooAtWFU]

So light goes backwards in this doodad?

Nope. Neither does light does not move faster than the speed of light, just phase groups. These crests and troughs of the light are features of the wave, but not any sort of signal or material in and of themselves. It's just an abstraction. Think of it this way: if you had two people a light-year apart, and they both raised their hands into the air at the same time to do The Wave, would you say that they sent a signal faster than the speed of light? If you had a one-light-year-long string of lights, and you rigged them all so they turned on at the exact same moment (presumably using some sort of countdown), would you say they've sent a signal faster than the speed of light? (Have you, in fact, sent a signal with infinite speed?) No, you haven't. You've gotten an abstraction to move faster than the speed of light, but that's not really very interesting for physics.

Re:

[Chris Burke]

Yeah, the metaphor that helped me understand was pointing at an object many light years away with a very bright laser. If you wave the laser back and forth, the dot on the distant object would appear to move faster than light, but the dot isn't an object, it's the point at which the laser beam hits the object. The laser itself is moving at c and no more.

Re:

[SEE]

Negative and with an absolute value greater than or equal to 1 (keeping the group velocity equal to or less than c, but antiparallel to the phase velocity -- geometrically parallel with an opposite-direction vector.)

Re:

[SEE]

Er, neverind, New Scientist is reporting the number as -0.6. Clearly I fucked up my understanding. (Again, for those following my recent posts.)

Re:Negative or less than one?

[$RANDOMLUSER]

> Come on doofus, C is the the speed of light. How can light go faster than itself ???

Perhaps it could go as fast as his post went over your head.

Re:

[Jarjarthejedi]

C is the speed of light in a vacuum. Light in air travels at C velocities. Light in liquids travel even more C. While there are legitimate concerns about the possibility of anything, light included, traveling faster than C your question is irrelevant as the light is not 'traveling faster than itself' but rather traveling faster than it would in a vacuum. It's like saying 'The plane's Cruise speed is 300 MpH, how can it cruise faster than itself?'

Finally...

[Druox]

An invisibility cloak..

For the first time, I may have a real shot at seeing real life naked boobies

Re:

[hobbesx]

For the first time, I may have a real shot at seeing real life naked boobies

Have you tried just looking down?

Re:

[StarfishOne]

Just wait until a Predator knocks on your door.. demanding that you return his suit ;O

Re:

[zobier]

I think this guy found some http://slashdot.org/~Archangel+Michael/journal/656 33 [slashdot.org].

This should come in handy...

[Da Fokka]

!!!tsoP tsriF

Invisibility cloak?

[namityadav]

I can understand how this material can make an item stealthy from radars and all. This material can be used to bend / deflect the rays so that they never return to the radar. But the same concept does not an invisibility cloak make. If a cloak deflects light, then the human eye will see a missing spot (Because, unlike the radar, an eye would see everything else around the cloak).

So, for a cloak to be invisible, we need it to pass light from the other end of the cloak. For this, the cloak would need to know the geometrical shape that it has currently, absorb light coming from one end, and forward it to a light emitting object on the other end of the cloak. The problem then will be that the cloak would need to know where the "eye" is to be able to map back and front ends correctly.

Am I talking non-sense here?

Re:Invisibility cloak?

[Born2bwire]

What left-handed materials do is that it bends light in the opposite sense that we are accustomed. For example, if you place a pencil in a glass of water, the refraction of light will make the pencil appear shallower than its true position. If the pencil is placed in a left-handed medium, then the pencil will appear deeper than it actually is.

What happens is that left-handed (aka negative refractive index) materials will bend light away from the surface of the material instead of towards it. So making an "invisibility cloak" is not that hard. First off, to solve the problem of knowing where the eye is, you simply make the surface of the material symmetric. So for a three-dimensional object, the left-handed material needs to be spherically symmetric. They have produced an example in the microwave region for a cylindrically symmetric configuration. But the cylindrical symmetry means that the shroud will only work for certain polarizations of light.

So what happens is that when light hits the curved surface, instead of being bent in towards the center, it is bent outwards. If the refractive properties of the medium are properly tuned, what you end up doing is bending the light around the obstacle such that it leaves the medium in the same path that it would have without the obstacle. So the "invisibility cloak" works by bending light around and emitting it so that the light behaves as if there was no object. Since the medium is symmetrical, it does not matter where the source and receivers are.

For a true cloak to work will require a really neat feat of engineering because the refractive properties of the material must be constantly adjusting with the movement of the cloak.

Re:

[Denial93]

Thank you for your explanation. So we're not talking about a hypothetical cloak, we're talking about hypothetical spherical vehicles that cannot use any conventional means of propulsion because that'd defeat their invisibility.

The UFO enthusiasts are going to be all over that one.

Re:

[penguinwhoflew]

You've never seen a hamster ball, have you?

Re:

[zobier]

Bingo

Re:

[Chris Burke]

So for a three-dimensional object, the left-handed material needs to be spherically symmetric. ...
For a true cloak to work will require a really neat feat of engineering because the refractive properties of the material must be constantly adjusting with the movement of the cloak.

A true cloak sounds hard, so would the easiest proof of concept then be the Invisibility Hamster Ball?

But the cylindrical symmetry means that the shroud will only work for certain polarizations of light.

Sounds like a weakness. Does

Corrections

[bw_bur]

Some of what you say is correct, but you're missing a fairly vital point.

There are several versions of invisibility floating around, but the most promising one (proposed by Pendry, Smith and Schurig) and the only one, as far as I'm aware, to have actually been demonstrated, DOES NOT USE NEGATIVE INDEX MATERIALS! There seems to be a great deal of confusion on this point (not helped by the summary above).

The cloak and the negative refractive index are both made possible by the advent of metamaterials. How

Re:

[stevelinton]

Yes and no. The cloak is actually rigid, and fairly thick, not anything you might actually wear as a cloak.
Incoming light (or, in actual devices built so far, incoming microwaves) from any direction at all, are bent around the object in the middle of the cloak
and emerge on the other side just as if the object (and cloak) were not there,

Re:

[Inda]

So, for a cloak to be invisible, we need it to pass light from the other end of the cloak.

Like a sheet of glass?

Am I talking non-sense here?

It's no good asking me, I only come here for the women.

Re:

[ruiner13]

Since the wavelengths of light are all refracted differently, I don't think this would make a very good cloak. By the time the light reached someone's eyes, the colors would look funky. It would be like looking at the light coming out of a prism, I'd think. When they come out with a medium that refracts light equally among all wavelengths (or at the very least across all the visible spectrum), then it could be used for cloaking.

On the other hand, I can see how this could be used for optic hardware, as th

Group vs. Phase Velocity

[Jazzer_Techie]

When one talks about a wave propagating through a medium, there are two velocities that one usually considers, the group velocity [wikipedia.org] and the phase velocity [wikipedia.org]. The group velocity is the speed at which energy and information are moving. (This isn't always true, but for most materials it is or is a good approximation.) The phase velocity is how fast a "phase" (a feature like a crest) appears to be moving.

A good way to visualize the difference is to think of a ocean waves hitting a wall at an angle. The speed which with the wave itself is moving is the group velocity, but if you look at the wall, you will see the crests moving along at a different speed. (If you have trouble seeing that, make a little sketch.) There is also a nice Java applet [publicliterature.org] (GPLed!) here, which does a good job of illustrating the difference

Re:

[bcrowell]

And it's important to point out that the material they're talking about has a negative phase velocity.

If you had a material with a negative group velocity, it would violate causality, because the information would get to its destination before it was transmitted. (In fact, any material with a group velocity n<1 would also violate causality, because according to special relativity, there would be a frame of reference in which the reception came after the emission.)

A few years ago, when the first news a

So the pencil bends the other way now?

[jpellino]

Never mind what this does to the coin-in-the-bowl-of-water trick!

Sheesh.

Transcript from Experiment

[jomama717]

• Scientist 1: Has anyone seen Helmut?
• Scientist 2: No, that's odd. I'll ask Frau Meier.
• Scientist 2: She says the lab... it just came alive and took him.

Re:Transcript from Experiment

[tsotha]

Scientist 1: If he bleeds, we can kill him.

What we need now: SEP fields

[gardyloo]

These metamaterials have a long and interesting history (many posts here on slashdot and elsewhere) -- long because they were predicted a while ago by Veselago, and interesting because of the recent interest due to Pendry's production of workable devices in electromagnetic fields. There are even meta-materials being produced for acoustics problems, too.
      However, what I'm really looking forward to is a Somebody Else's Problem device -- this will make all of the other foophraw unnecessary.

Nothing exotic about negative refractive index

[u19925]

There is nothing exotic about negative refractive index. It is trivially achievable in real life experiments, albeit not at optical frequencies. All information about the light falling on any surface can be captured if we can digitize electromagnetic waves at sampling rate which is twice the bandwidth. At optical wavelengths, this would be trillions of samples per second at each sensor and you will need multiple sensors spatially distributed across a surface. At radio frequencies with only a few mega hertz

Future Slashdot Article

[KoldKompress]

"German Scientists devestated after loosing non-reflective material"
One scientist quoted: "I just put it down here and now.. I can't find it!"

Original site of the researchers...

[thrill12]

...here [uni-karlsruhe.de], gives (under metamaterials) a good example of what negative refraction is here [uni-karlsruhe.de]

Re:

[mindriot]

Also, there's a paper [arxiv.org] available that provides more details.

Is this the actual research paper?

[starseeker]

http://arxiv.org/abs/physics/0607135 [arxiv.org]

From back in August?

Re:

[ultracool]

Papers are typically submitted to arxiv.org at the time of submission to a journal. If accepted, it usually appears in the particular journal several months later. The paper was published in Optics Letters just this week, though it was posted on arxiv.org in August:

http://ol.osa.org/abstract.cfm?id=119886 [osa.org] You have to keep in mind that before Arxiv.org papers (or any other pre-print archives) appear in a journal, you can't guaranteed that they have passed the peer-review process.

Peril Sensitive Sunglasses?

[Infernal Device]

Maybe now I'll feel safe when driving on the freeway!!

negative mass

[oohshiny]

Good. Now, if they could just start creating negative mass objects, then we'd be getting somewhere in terms of space travel.

Camera lenses

[AK Marc]

I would see an immediate use (presuming reasonable cost) in using something like this in camera lenses to combat chromatic aberration. Regular lenses bend light differently at different wavelengths so that the various colors don't focus exactly. With something that has a negative refractive index, the light could be passed through a set of these lenses to get the focal point to a single point.

Re:Camera lenses

[nokiator]

Technically, this is true, but I am not sure about the reasonable cost part. It is also possible to correct chromatic aberration using diffractive lenses which require much less exotic (at least completely passive) technology. Canon has been able to take the concept of diffractive optics technology [canon.com] to market to manufacture some relatively compact telephoto lenses but even after many years of production, DO lenses are still quite expensive [bhphotovideo.com].

Re:

[bobaferret]

Is it the fact that they are diffractive optics that make them expensive, or just the fact that they are cannon lenses?
this lens [bhphotovideo.com] is probably a better example for the average bear. Twice as expensive as it's nearest realative, but it's also 2" shorter. And that can make a big difference when your walking around knocking into stuff. Is it worth it? don't know, is the picture quality any better? don't know. I would assume so, or why sell the thing at all.

cloak of invisibility -- maybe not

[bcrowell]

I could be wrong, but if I'm understanding the physics properly, then there's a substantial barrier to using this technology for invisibility: all these meta-materials are highly dispersive, so the effect is unlikely to work over any significant range of wavelengths.

Hasn't this already been done?

[MrSteveSD]

This article is from 2005 http://physicsweb.org/articles/news/9/4/12 [physicsweb.org]

speed gun avoidance?

[binarybum]

according to the wiki entry on negative RI in metamaterials, "The Doppler shift is reversed (that is, a light source moving toward an observer appears to reduce its frequency)"

    Does this mean if I wrap my car in this stuff, the faster I drive, the slower radar guns/lasers will clock me at? (assuming the material has -RI at those lambdas)

Detail finer than the wavelength of light...

[gorehog]

Does this mean that Heisenberg's Uncertainty is no longer uncertain?

I always thought that the reason you couldn't know both speed and position was because the energy of the photon changed the position of the observed particle. Now, if you can see detail from in a range that is a fraction of the wavelength of light then aren't you also observing detail from a place where the photons aren't interacting with you?

That is to say...

If uncertainty is the space under the curve of a cycle of light,
and
you are able t

What of holographic lenses?

[mattr]

I remembered that a hologram of a lens could act as a lens and wondered whether a computer designed hologram could create one with negative refractive index. (Not having a solid grounding in optics makes one ask such dumb questions.)

Anyway I don't know the answer but found this page [mit.edu] which explains both holographic lenses and negative refraction and references Pendry. One of the things it states (concerning the "perfect lens" of Pendry that is possible with negative refraction materials) is:

For example, the

fractional index?

[dheera]

"Dolling determined the refractive index of the material by measuring the "phase velocity" of light as it passed through. His measurements show the structure has a negative refractive index of -0.6 for light with a wavelength of 780 nm.

This value drops to zero at 760 nm and 800 nm, and becomes positive at longer and shorter wavelengths. Previously, the shortest wavelength at which a negative refractive index had been demonstrated was 1400 nm. "

how is this possible? fractional indices would imply that the li

The emperor's new clothes

[j_square]

Metamaterials and the concept of negative index of refraction are likely the cold fusion equivalents of this decade...

There are several weak points in this whole business of "Harry Potter cloaks" where physicists with little experience in electromagnetics (and even less in radar cross section reduction) go astray. To list but a few points:

Irrelevance of group velocity
It has long been known that effects like anomalous dispersion in resonant media can render classical group velocity concepts irrelevant. Sever

No pics?

[Zaatxe]

Nothing to see here, move along...
Oh, now I get it... how to photograph invisible objects? Dumb me!

visual example

[namekuseijin]

In case anyone is wondering what a negative index of refraction would look like, this is a very good start:

http://www.opticsexpress.org/abstract.cfm?id=88325 [opticsexpress.org]

Examples (including avi's) rendered in Povray, the free raytracer. One of the authors is Chris Hormann, one of Povray's main code contributors.

Wikipedia

[benhocking]

Wikipedia does a good job describing refraction [wikipedia.org] and the refractive index [wikipedia.org]. You should try to understand refraction before trying to understand the refractive index.

Re:

[wolfgang_spangler]

Is there a layman's explanation around somewhere?

Perhaps Wikipedia [wikipedia.org]?

Or Answers.com [answers.com]?

Or one of the million other places? Is it honestly that much harder for you to type the query into google than to post it to slashdot?

Re:Can someone explain a refraction index?

[VorpalEdge]

If I check another site, I lose my excuse for bashing the poor quality of the article. That's just not an option.

Re:

[Anonymous Coward]

Short version: light travels at different speeds through different substances. It's faster in air than it is in water or glass. When it strikes a boundary between two substances -- say, air and glass -- at an angle, it will turn slightly, because one edge of the beam hits the new substance sooner than the other, and will slow down (or speed up) sooner.

This is why you sometimes see two of the same fish when you look at the corner of a fish tank. The light gets bent as it travels from water to glass, and a

Re:

[Gilmoure]

Don't forget Jethro Tull. He invented the seed drill.

Re:Can someone explain a refraction index?

[Romberg]

I thought Jethro Tull invented the aqualung.

Re:

[Viper Daimao]

I always wondered why you'd put cotton in gin, I usually prefer vermouth.

Re:

[athena_wiles]

Refractive index basically describes how fast light moves through a material. That's the "speed at which they propagate" part of the quote you cited - in materials with a high refractive index, which you might think of more "optically dense" or preventing more barriers to the "movement" of the light, light travels more slowly than it does in materials with lower refractive indices.

When you have two materials with different refractive indices up against each other, light bends by some angle (the angle depe

Re:

[Fred_A]

I'm sure you've seen the effect where you put a straw or a pencil into a partly-full glass of water (if you haven't, go try it) and the straw/pencil appears to be bent - this property of refractive indices is what's causing this phenomenon.

Interestingly, when you try to push a straw through a block of glass, the straw bends relatively to the strength that you apply therefore proving that the bloack's refraction varies with pressure. :)

Re:

[exp(pi*sqrt(163))]

For all I know, it could mean they bend backwards while doing spirals or figure eights.

This is exactly [wikipedia.org] what light does.

Re:Can someone explain a refraction index?

[radtea]

Furthermore, it doesn't explain what the basic properties of a positive refraction index are (aside from saying that it's normal), let alone what negative indexes could do.

In ordinary optics, refractive index is the ratio of the velocity of light in vacuum (c) to the velocity in the material (v):

n = c/v

Since v <= c, n >= 1 is always true.

But light, being wavelike, has two velocities associated with it: the phase velocity, which is the velocity of an individual crest in a monochromatic light wave, and the group velocity, which is the velocity of a wave packet consisting of many frequencies. Depending on which velocity you care about, and how you deal with wave packets, it appears that you can extend the definition of refractive index in such a way that negative refractive index is meaningful. The discussions of this that I have seen online are uniformly confusing, so I'm not clear on exactly what is going on, although it is clear that negative extended refractive indices do make sense.

One analogy to think about is the conventional definition of resistance: R = V/I. Clearly by this definition resistance is always positive. But if instead you think of resistance as being the slope of the V/I curve, it is clearly possible for a device whose (conventional) resistance decreases with increasing current it is possible to have a slope that is negative, and this can be treated as "negative resistance". Tunnel diodes exhibit this effect.

If one were to be gloriously pedantic about this, one would only use the terms "negative extended refractive index" and "negative extended resistance", because "negative refractive index" and "negative resistance" are confusing oxymorons to the vast majority of people in the world who are at best familiar with the conventional definitions. And in fact, we usually do make this kind of distinction. We use terms like "electric car" because "car" means "internal combustion engine hydrocarbon-powered road vehicle" to the vast majority of people. Therefore headlines like, "New Car Does Not Need Gasline" would be obviously misleading and confusing if they actually meant "New Electric Car Does Not Need Gasoline."

Hang in there.

[CaseyB]

When you get to high school you'll cover this stuff in physics class.

Re:

[Alsee]

When you get to high school you'll cover this stuff in physics class.

Maybe, or maybe not. [google.com]

-

Re:

[gardyloo]

Does "[The researcher]" have a name? Has this work been published in a peer reviewed article of repute?

If you'd read the article, the answers would become clear:

1) Yes: Gunnar Dolling;
2) Dunno. He has many peer-reviewed articles in Science and comparable journals; this one first showed up in June 2006 on xarchiv, but is published in the Journal of Optical Networking, Jan 2007: https://www.osa-jon.org/abstract.cfm?id=119886 [osa-jon.org]

Re:Negative OK, but why |-1| ?

[Born2bwire]

Another way to describe the refractive index is in terms of the square root of the relative permeabilities and permittivities. In a negative refractive index, epsilon and mu are both negative. However, the refractive index is the square root of the product of these two. So they probably just retain the sign on the refractive index to show this important characteristic.

Basically all it means is that light is going to bend opposite of what we would normally expect. Instead of bending towards the interface, light will bend away from the interface. There's no fancy u-turns or anything like that. The negative sign is purely a consequence of the convention by which we choose our cross products when it comes to the vector form of Maxwell's Equations. Normally we use a right-hand convention, but a metamaterial behaves using the left-hand convention. This negative sign is one way of achieving the same effects using the right-hand vector convention.