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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."
... for stalkers worldwide !
The GNAA has discover a giant black manhole
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.
quis custodiet ipsos custodes
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)?
--josh
I, for one, welcome our new invisible overlords... wherever you are...
small penis jokes at physics conventions.
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?
Nothing to see here. Move along.
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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!
Give a man a fish and you have fed him for today. Teach a man to fish, and he'll say "WHERE'S MY FISH, YOU IDIOT?"
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).
Ben Hocking
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Wikipedia does a good job describing refraction and the refractive index. You should try to understand refraction before trying to understand the refractive index.
Ben Hocking
Need a professional organizer?
An invisibility cloak..
For the first time, I may have a real shot at seeing real life naked boobies
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!!!tsoP tsriF
Does a lifetime of German cuisine and German adult videos boost IQ?
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?
When one talks about a wave propagating through a medium, there are two velocities that one usually considers, the group velocity and the phase velocity. 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 (GPLed!) here, which does a good job of illustrating the difference
Never mind what this does to the coin-in-the-bowl-of-water trick!
Sheesh.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
while [ 1 ]; do echo -n -e "\xe2\x95\xb$((($RANDOM&1)+1))"; done
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.
V= C/N , therefore light will go backwards? will this material act like a mirror?
"School" is an even better place than Wikipedia to learn things. The OP might want to try that sometime, too.
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.
When you get to high school you'll cover this stuff in physics class.
http://en.wikipedia.org/wiki/Overlord_meme
- Give a man a fire and he's warm for a day, but set him on fire and he's warm for the rest of his life.
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
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
"German Scientists devestated after loosing non-reflective material"
One scientist quoted: "I just put it down here and now.. I can't find it!"
This was on Scientific American a while ago...http://www.sciam.com/article.cfm?articleID=0 00A27C4-0C1B-1C5E-B882809EC588ED9F
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.
...here, gives (under metamaterials) a good example of what negative refraction is here
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http://arxiv.org/abs/physics/0607135
From back in August?
"I object to doing things that computers can do." -- Olin Shivers, lispers.org
Maybe now I'll feel safe when driving on the freeway!!
"My God...it's full of trolls!"
Good. Now, if they could just start creating negative mass objects, then we'd be getting somewhere in terms of space travel.
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.
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As I understand it, post secondary education has been completely free for the past 200 years.
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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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.
Ben Hocking
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...you can count me in!
I can now see through all your comments!
It's gonna be a bitch to track down in the wild...
So more important to me is will we get slow glass out of this? Slow glass is glass that light can take really (years) long periods to pass through. The idea for slow glass comes from a great short story by the late Bob Shaw called Light of Other Days. See the full text at:
_ archive/shaw/shaw1.html
http://www.scifi.com/scifiction/classics/classics
And could slow glass function as a "type" of invisibility or camouflage in this context?
Thanks,
PaGeN
When a Ball Dreams, It Dreams it's a Frisbee.
FTA: "The team has not yet observed some of the other exotic effects possible with a negative refractive index, such as the ability to bend light backwards." Last time I czeched, this was a device called a "mirror".
"Freedom in the USA is not the ability to do what you want. It is the ability to stop others from doing what THEY want"
This article is from 2005 http://physicsweb.org/articles/news/9/4/12
Oops! Not anymore it doesn't...
My my, she does have nice lenses.
The race to build blah blah blah has been won ... The advance could lead to blah blah blah.
That's great and all, but let us know when you actually accomplish something.
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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)
ôó
Maybe I'm just blind, maybe I'm missing somthing here, but if it actually worked, wouldn't he just be able to say "hey, where the fuck did my mirror go ?!" instead of measuring light through some fancy device ?
:/
Please forgive me if I missed somthing, but I can't help but think about the kid that tells me I can't see him "because he's invisible" as I'm looking right at him.
Wanna fight ? Bend over, stick your head up your ass, and fight for air.
Those bastards'll need to dump waste heat at some point. Can't hide that forever!
I'd love to see the looks on the faces of people that have Limo Tint on their windows when I pull up to the stop light with some of this stuff.
Wanna fight ? Bend over, stick your head up your ass, and fight for air.
It doesn't make a U-Turn. Things that make light do U-turns are called mirrors.
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 to see detail finer than that wavelength
then
are you seeing into the area of uncertainty?
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 from detection.
in. Hence the spam...
Anyway I don't know the answer but found this page 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:
...any photos?
*duck*
"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 light is going faster than light in a vacuum. i would expect negative index materials to have indices of less than -1 and no material to be able to have anything between -1 and 1.
..so now i can look bald instead?
Is tht a step up in the food chain???
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. Several authors seem to lack an understanding of the inherent assumptions when equaling the group velocity with a power or information transfer speed. Thus an interpretation leading to an "equivalent" negative index of refraction can be misleading.
Bandwidth
The bandwidth of these materials is inherently small. There is also often a significant loss as well.
Misuse of models
The assumption of monochromatic and plane waves interacting with an infinite structure will be like pressing a square peg into a round hole when dealing with some cases. For example, it is well-known that a simplistic plane-wave model is invalid when dealing with lossy materials (apart from normal incidence).
Publications in out-of-field journals
It is clear that a lot of the metamaterial material has been published in journals that are outside the typical antenna or microwave area, such as Nature, Science, and Phys. Rev. This could potentially lead to deficient papers slipping through, due to lack of a proper review. An example of something that hopefully would have been curbed in an IEEE journal is a Phys. Rev. paper [*] that showed a transmission vs. frequency plot with a dynamic range of 1600 dB! (The range of scale of the size of the universe compared to the Planck length is dwarfed by this...). There are numerous examples of publications without even the most basic sanity checks performed by the authors and the reviewers. The situation has been bad enough for the microwave field, now it is unfortunately spreading to optical frequencies.
[*] R.W. Ziolkowski and C.-Y. Cheng, "Existence and design of trans-vacuum-speed metamaterials", Phys. Rev. E, 68, 026612, 2003.
Peer review endangered
The field of metamaterials has now grown to such a volume that a wholly separate sub-science or "sect" with its own special issues and conferences, etc. has formed. There is an inherent problem with this, since the peer review process will be endangered. The people most knowledgeable within the subject are by definition those that are active within the subject, and fewer outside reviewers will be used after a while.
"Publication by news releases"
Several of the groups within this field are heavy on marketing their results as revolutionary. In the present "publish or perish" environment it is very important to secure funding, and gullible grant-givers are abundant...
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.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
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 into the near infrared as a very bright near infrared source will excite the rods or cones (not sure which it is) a tiny amount.
Nothing to see here, move along...
Oh, now I get it... how to photograph invisible objects? Dumb me!
So say we all
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. However, this is all they have in common!
They are called mirrors.
Actually I found a picture of it which I'm posting here for your benefit:
Pretty cool, huh?
What if the Hokey Pokey really is what it's all about?
Does your inability to use the correct form of to/two/too stem from being an idiot, or does it just violate your cultural values to stoop to using the correct word?
Is that the best reposte you can come up with? Actually my wireless keyboard often omits characters (as you can see from other words in the post) and I don't waste my time trying to corret them. If that makes me an idiot by your definition then so be it. Doofus.
Light travels about 310 times C in a cesium vapor.
The cesspool just got a check and balance.
If you care so little about what you write, that you would use a peripheral that mangles your words, why don't you just throw all of your keyboards into the ocean and shout at the screen?
How old are you...12? I'm through with this stupidity.
I for one welcome our new, possibly even non-human invisible overlords.
(come on now, you know they found this in one of the closets they never before opened in the crashed saucer from Roswell... right next to the purple sports jacket, busted vacumn cleaner and running shoes"
If a pion (n-) collides with a proton in the woods & noone is there to hear it, does lamdba decay into the source pa
if someone could explain in intelligble terms, what is the difference between velocity, phase velocity and group velocity ? (if u can do that, perhaps "mode" as used in acceptable to a fiber optic would be next)
In case anyone is wondering what a negative index of refraction would look like, this is a very good start:
5
http://www.opticsexpress.org/abstract.cfm?id=8832
Examples (including avi's) rendered in Povray, the free raytracer. One of the authors is Chris Hormann, one of Povray's main code contributors.
I don't feel like it...
Not to mention the fake beard and glasses...
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
Here's an article which gives a good explanation of why this is important. Remember, scientific investigation is limited to what we can observe. Anything that allows us to see more, see better, is usually followed by a slew of advances in a variety of scientific feilds.
http://physicsweb.org/articles/news/9/4/12
"Conventional, positive-refractive-index lenses create images by capturing the light waves emitted by an object and then bending them. However, objects also emit "evanescent" waves that contain a lot of information at very small scales about the object. These waves are much harder to measure because they decay exponentially and never reach the image plane -- a threshold in optics known as the diffraction limit.
In 2000, John Pendry of Imperial College in London suggested that a material with a negative refractive index -- that is, one that bends light in the opposite direction to an ordinary material -- could capture and "refocus" these evanescent waves. This idea of a perfect lens or "superlens" came over 30 years after Russian physicist Victor Veselago first speculated that negative index materials could exist. In such a superlens, electromagnetic waves that reach the surface of a negative refraction lens excite a collective movement of surface waves, such as electric oscillations -- also known as "surface plasmons". This process enhances and recovers the evanescent waves."