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Material With Negative Refractive Index Created

kdawson posted more than 7 years ago | from the seeing-right-through-it dept.

Science 210

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."

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It's good news ... (3, Funny)

jfclavette (961511) | more than 7 years ago | (#17291628)

... for stalkers worldwide !

Re:It's good news ... (0, Offtopic)

ThatsNotFunny (775189) | more than 7 years ago | (#17291748)

Now that this has been invented, can we get a patch for Sneak King?

Why do Germans seem ... (0)

Anonymous Coward | more than 7 years ago | (#17291882)

Why do German scientists seem to accomplish more breakthroughs in science and technology than other cultural groups?

Does a lifetime of German cuisine and German adult videos boost IQ?

Re:Why do Germans seem ... (5, Funny)

anonymous22 (826938) | more than 7 years ago | (#17292130)

It's the beer.

Re:Why do Germans seem ... (0)

Anonymous Coward | more than 7 years ago | (#17292428)

Because you seem to be focusing on German Scientists.

If anything would be affecting the research or career paths of German scientists and the students they come from, then it would be cultural influences such as the availability of jobs, the prestige presented by getting such jobs, and the individual drive to gain knowledge and understanding.

Re:Why do Germans seem ... (-1, Flamebait)

Schraegstrichpunkt (931443) | more than 7 years ago | (#17293220)

Because they got rid of most of their Jewish population. </sarcasm>

Free University (3, Informative)

DerangedAlchemist (995856) | more than 7 years ago | (#17293606)

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

In other news (0, Funny)

Anonymous Coward | more than 7 years ago | (#17291640)

The GNAA has discover a giant black manhole

yes, but RTFA, they were not first. (3, Informative)

PrinceAshitaka (562972) | more than 7 years ago | (#17291648)

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. (4, Informative)

wolfgang_spangler (40539) | more than 7 years ago | (#17291784)

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. (5, Funny)

Anonymous Coward | more than 7 years ago | (#17292038)

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. (4, Funny)

LearnToSpell (694184) | more than 7 years ago | (#17292374)

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

Re:yes, but RTFA, they were not first. (1)

alexhard (778254) | more than 7 years ago | (#17293154)

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.
I, too, have achieved this, but the solution will not fit the empty space in this comment.

Visible spectrum and cones (5, Informative)

benhocking (724439) | more than 7 years ago | (#17291794)

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 (5, Funny)

silentounce (1004459) | more than 7 years ago | (#17292490)

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:Visible spectrum and cones (0)

Anonymous Coward | more than 7 years ago | (#17293526)

Would this mean that it would be possible to build an "invisibility cloak" that only tetrachromats [wikipedia.org] can detect?

Tetrachromats need not apply (2, Interesting)

benhocking (724439) | more than 7 years ago | (#17293754)

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 tetrachromat is neither necessary nor sufficient.

Re:yes, but RTFA, they were not first. (1)

DJ.Flecktarn (1028326) | more than 7 years ago | (#17292502)

Yes. ~700 is red. This is why the name of the article is "Red light debut for exotic 'metamaterial'". It's a pun.

GNAA (-1, Troll)

Anonymous Coward | more than 7 years ago | (#17291656)

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does this mean? (3, Interesting)

jforest1 (966315) | more than 7 years ago | (#17291688)

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

Re:does this mean? (0)

Anonymous Coward | more than 7 years ago | (#17292334)

Hrm.. microwave guns. So much better than waterboarding, and you can do it to a huge group of folks at once. Just imagine, cops no longer needing fire hoses and tear gas to break up anti-war protests and such. It'll be great.

obligatory (3, Funny)

owlnation (858981) | more than 7 years ago | (#17291736)

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

Re:obligatory (2, Interesting)

MollyB (162595) | more than 7 years ago | (#17292168)

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:obligatory (0)

Anonymous Coward | more than 7 years ago | (#17292458)

Sir/Ma'am, please hand in your geek card. you have obviously never watched the Simpsons.

Re:obligatory (4, Funny)

Anonymous Coward | more than 7 years ago | (#17292528)

you must be new here...

Re:obligatory (3, Funny)

networkBoy (774728) | more than 7 years ago | (#17293364)

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

Wikipedia has your answer... (0, Redundant)

Otto (17870) | more than 7 years ago | (#17292554)

Re:Wikipedia has your answer... (1)

MollyB (162595) | more than 7 years ago | (#17292788)

Thanks, and to all the other helpful posters. I actually saw the episode referenced on fox reruns lately, too! Just didn't make the connection. Duh.

This will revolutionize... (4, Funny)

Anonymous Coward | more than 7 years ago | (#17291762)

small penis jokes at physics conventions.

Can someone explain a refraction index? (1)

VorpalEdge (967279) | more than 7 years ago | (#17291768)

FTA: "The refractive index describes the way the light waves bend when they enter and leave the material and the speed at which they propagate." However, this says little to nothing. "It describes the way light waves bend..." For all I know, it could mean they bend backwards while doing spirals or figure eights. 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.

Is there a layman's explanation around somewhere?

Wikipedia (5, Informative)

benhocking (724439) | more than 7 years ago | (#17291840)

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.

School (1, Funny)

Anonymous Coward | more than 7 years ago | (#17292270)

"School" is an even better place than Wikipedia to learn things. The OP might want to try that sometime, too.

Re:Can someone explain a refraction index? (1, Informative)

Anonymous Coward | more than 7 years ago | (#17291856)

Refractive index is a measure of several things:
(1) Speed of light in a material is (for normal materials where n>1) v = c/n
(2) Measure of how much light bends when it enters said material through something called Snell's law

Re:Can someone explain a refraction index? (1)

wolfgang_spangler (40539) | more than 7 years ago | (#17291880)

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? (5, Funny)

VorpalEdge (967279) | more than 7 years ago | (#17291980)

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

Re:Can someone explain a refraction index? (3, Informative)

Anonymous Coward | more than 7 years ago | (#17291998)

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 again from glass to air, resulting in two paths from the fish to your eye. This is also how lenses work.

So that's refraction. The refractive index is essentially a measurement of how much it bends when pssing into that substance.

(Honestly, I learned about refraction in third or fourth grade. What do they teach in schools these days?)

Re:Can someone explain a refraction index? (1)

kannibal_klown (531544) | more than 7 years ago | (#17292346)

(Honestly, I learned about refraction in third or fourth grade. What do they teach in schools these days?)
I learned it back then as well. I think it was around the time we were talking about concave and convex mirrors.

Then again, with the exception of stuff I've needed every day since (math, cursive writing, etc) I've forgotten much of what I've learned from those grades... except Eli Whitney for some reason.

Re:Can someone explain a refraction index? (1)

Gilmoure (18428) | more than 7 years ago | (#17292918)

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

Re:Can someone explain a refraction index? (1)

Viper Daimao (911947) | more than 7 years ago | (#17292954)

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

Re:Can someone explain a refraction index? (3, Informative)

athena_wiles (967508) | more than 7 years ago | (#17292010)

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 depends on how close the refractive indices of the two materials are). 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.

Basically, a negative refractive index changes/reverses the angle at which light bends, which can lead to some pretty funky optical effects. If you go to the wikipedia page on "Metamaterial" there's a diagram indicating this concept.

Does that help? It's not a precise technical definition by any means, but then, I don't think a precise technical definition is what you were asking for, hm? :-)

Re:Can someone explain a refraction index? (2, Informative)

exp(pi*sqrt(163)) (613870) | more than 7 years ago | (#17292036)

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? (-1)

Anonymous Coward | more than 7 years ago | (#17292060)

Well, for one thing, if you look at snell's law, a negative index of refraction seems to mean that light bends back away from the normal to the surface. but I think that might be a weird way of looking at it anyway.

I believe what this all is usually talking about is a dielectric band gap, which is when light of a particular frequency can't propagate (the frequency ends up imaginary, so it simply decays). Light isn't transmitted, which means it's reflected. Basically, the periodicity of the material prevents particular modes of electromagnetic waves from existing inside the material. Now, IAAMS, but I don't know a heck of a lot about photonics, except for what's in Joannopolous's book on the field. Looking through the index, I see nothing about negative refractive indexes or negative dielectric constants, but I have the feeling they're the same thing.

The more classical way to look at it is... hmm... impossible to draw in ASCII art.

Anyway, at the least... perfect reflection != invisibility... duh (not at you, the other people posting).

Re:Can someone explain a refraction index? (5, Informative)

radtea (464814) | more than 7 years ago | (#17292230)

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. (2, Interesting)

CaseyB (1105) | more than 7 years ago | (#17292454)

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

Re:Can someone explain a refraction index? (1)

dkarma (985926) | more than 7 years ago | (#17293616)

you watch a light beam go into water and be bent and dissipate
they just measure the speed and angle change through the medium i guess. for some reason this one lines the light up w/ the right part of the spectrum to let you see something like infrared i guess.

All right! (5, Funny)

morgan_greywolf (835522) | more than 7 years ago | (#17291774)

Nothing to see here. Move along.

Re:All right! (1)

flitty (981864) | more than 7 years ago | (#17291862)

HA! sorry, but that was quite funny.

Negative or less than one? (1)

wsanders (114993) | more than 7 years ago | (#17291788)

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? (5, Funny)

HotBBQ (714130) | more than 7 years ago | (#17291838)

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

Write it in Java.

Re:Negative or less than one? (5, Funny)

elzahir (442873) | more than 7 years ago | (#17292080)

No, he said _faster_

Re:Negative or less than one? (0)

Anonymous Coward | more than 7 years ago | (#17292854)

And it will be, if you're writing the C :)

Re:Negative or less than one? (0)

Anonymous Coward | more than 7 years ago | (#17292870)

hahahhahahhahaha oh MAN that's a good one. never woulda thought of that! my hat to you, sir!

Re:Negative or less than one? (1)

Schraegstrichpunkt (931443) | more than 7 years ago | (#17293544)

hahahhahahhahaha oh MAN that's a good one. never woulda thought of that! my hat to you, sir!

(Repeated because it applies just as well to the parent as to the grandparent.)

Re:Negative or less than one? (0)

Anonymous Coward | more than 7 years ago | (#17291984)

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

Re:Negative or less than one? (4, Funny)

$RANDOMLUSER (804576) | more than 7 years ago | (#17292254)

> 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:Negative or less than one? (2, Interesting)

Jarjarthejedi (996957) | more than 7 years ago | (#17292316)

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?'

Re:Negative or less than one? (-1, Flamebait)

Anonymous Coward | more than 7 years ago | (#17292674)

no you retard, C is Heat capacity, Carbon, Coulomb, Capacitance, etc., a lot of different things, but the speed of light is still c and not C.

Re:Negative or less than one? (1, Interesting)

Anonymous Coward | more than 7 years ago | (#17292710)

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

I think you'll find that C is the speed of light in a vacuum. In most media (i.e. everything we've found so far) light is actually slower than C. In fact, it's actually possible for particles to travel faster than the speed of light in a particular medium (see Cherenkov radiation [wikipedia.org] ) -- though so far, not faster than C.

Re:Negative or less than one? (1)

l2718 (514756) | more than 7 years ago | (#17292424)

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 here. The group velocity is the speed at which the information (and energy) contained in the wave travels. This can't exceed 'c' -- otherwise we'd have acausal physics.

Re:Negative or less than one? (1)

imsabbel (611519) | more than 7 years ago | (#17293502)

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

Re:Negative or less than one? (5, Insightful)

FooAtWFU (699187) | more than 7 years ago | (#17292494)

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:Negative or less than one? (1)

SEE (7681) | more than 7 years ago | (#17292592)

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:Negative or less than one? (1)

SEE (7681) | more than 7 years ago | (#17292670)

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

Finally... (5, Funny)

Druox (911165) | more than 7 years ago | (#17291842)

An invisibility cloak..

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

Re:Finally... (3, Funny)

hobbesx (259250) | more than 7 years ago | (#17293382)

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

Have you tried just looking down?

This should come in handy... (3, Funny)

Da Fokka (94074) | more than 7 years ago | (#17291852)

!!!tsoP tsriF

Re:This should come in handy... (1)

Paradise Pete (33184) | more than 7 years ago | (#17292092)

Parent post, while perhaps not the most clever of the jokes in this thread, is not actually off-topic.

Invisibility cloak? (4, Insightful)

namityadav (989838) | more than 7 years ago | (#17291966)

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? (5, Interesting)

Born2bwire (977760) | more than 7 years ago | (#17292246)

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:Invisibility cloak? (1)

Denial93 (773403) | more than 7 years ago | (#17292942)

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:Invisibility cloak? (0)

Anonymous Coward | more than 7 years ago | (#17293142)

Not exactly. The refraction will be spherical, the object doesn't need to be. It simply means that light coming in at any angle must be refracted around the object and come out with the same orientation as it came in. It bends around the object to hide.

Re:Invisibility cloak? (1)

stevelinton (4044) | more than 7 years ago | (#17292368)

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:Invisibility cloak? (0)

Anonymous Coward | more than 7 years ago | (#17292508)

Does a piece of glass need to know which way you're looking at it? Does a cylinder dipped into a stream need to know which direction the water is flowing for the water to go around it seamlessly? (OK, there's actually turbulence, but let's assume we can do so perfectly, because light isn't actually a fluid.)

The idea behind the invisibility cloak is that you provide a material that can bend light right around the object, passing it straight through without deflecting it. Thus all light beams behave exactly the same as if there's no object there at all.

Whether it's practical or not is a different question, but in theory, it's certainly a possibility.

Re:Invisibility cloak? (1)

Inda (580031) | more than 7 years ago | (#17292600)

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.

Group vs. Phase Velocity (5, Informative)

Jazzer_Techie (800432) | more than 7 years ago | (#17291986)

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:Group vs. Phase Velocity (2, Interesting)

bcrowell (177657) | more than 7 years ago | (#17293212)

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 articles started appearing about n<0 microwave media, a music prof I know e-mailed me excitedly about whether I'd heard about the new technology for time travel. He'd have been right, if it was group velocity.

So the pencil bends the other way now? (2, Informative)

jpellino (202698) | more than 7 years ago | (#17292034)

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

Sheesh.

Transcript from Experiment (4, Funny)

jomama717 (779243) | more than 7 years ago | (#17292142)

  • 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 (3, Funny)

tsotha (720379) | more than 7 years ago | (#17293686)

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

Re:Transcript from Experiment (1)

jomama717 (779243) | more than 7 years ago | (#17293776)

Woohoo! - somebody got it :)

Nu Scientist (-1, Flamebait)

Anonymous Coward | more than 7 years ago | (#17292226)

I don't believe it. Why? Source: Nu Scientist.

I won't even click the link for details, that would help in slashdot's efforts to drive traffic to Nu Scientist.

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

Re:Nu Scientist (1)

gardyloo (512791) | more than 7 years ago | (#17292612)

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]

What we need now: SEP fields (3, Insightful)

gardyloo (512791) | more than 7 years ago | (#17292232)

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.

Mirror? (0)

Anonymous Coward | more than 7 years ago | (#17292252)

V= C/N , therefore light will go backwards? will this material act like a mirror?

Nothing exotic about negative refractive index (1, Informative)

u19925 (613350) | more than 7 years ago | (#17292350)

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 bandwidth, this can be done and is being done routinely (by radio astronomers in VLBI experiments) for almost 30 years. Once you digitize the signal, you can simulate any refractive index as you wish using a computer. Mathematics and computing power are the limit.

Negative OK, but why |-1| ? (1)

kanweg (771128) | more than 7 years ago | (#17292576)

The refractive index is the ratio between the speed of light/speed of light in medium. Because c is the top speed, refractive index of air is close to 1, and from there it is only up.

Now, with a negative breaking index, light isn't just refracted (bent) at an interface (transition from one refractive index to the other), but actually makes a U-turn (V-turn might be a better term). But we don't expect the light to go faster than c, do we? (Now that would make a couple of things possible!).

So, what's up with the reported value of -0.6?

Bert

Re:Negative OK, but why |-1| ? (4, Insightful)

Born2bwire (977760) | more than 7 years ago | (#17292802)

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.

Future Slashdot Article (2, Funny)

KoldKompress (1034414) | more than 7 years ago | (#17292752)

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

Yuo Failn It! (-1, Offtopic)

Anonymous Coward | more than 7 years ago | (#17292796)

future4. Even Would you like to r3asons why anyone ones in software

Original site of the researchers... (4, Informative)

thrill12 (711899) | more than 7 years ago | (#17292988)

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

Peril Sensitive Sunglasses? (1)

Infernal Device (865066) | more than 7 years ago | (#17293188)

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

negative mass (1)

oohshiny (998054) | more than 7 years ago | (#17293248)

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

Camera lenses (4, Interesting)

AK Marc (707885) | more than 7 years ago | (#17293514)

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.

cloak of invisibility -- maybe not (2, Interesting)

bcrowell (177657) | more than 7 years ago | (#17293612)

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.
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