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Comments: 125 +-   Negative Refractivity for Optical Computing on Wednesday August 28 2002, @08:16AM

Posted by michael on Wednesday August 28 2002, @08:16AM
from the making-the-impossible-possible dept.
science
zero_offset writes "This article in EE Times details Purdue's efforts to create a material with negative refractivity. One of the important results would be the ability to create optical computers due to the effect's tendency to amplify and focus light at wavelengths larger than the thickness of the nanowires used in the transmission system. Purdue's School of Electrical and Computer Engineering's Vladimir Shalaev says, "Using these plasmonic nanomaterials, we hope to directly manipulate light, guide it around corners with no losses and basically do all the fundamental operations we do with electronic circuits today, but with photons instead." Nanowires, surface plasmon polaritons, optical computers, nanoscale metamaterials, unnatural refractivity -- what's not to like?" We did a story on the first material known to have a negative index of refraction last year.
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  • Well, there goes Moore's law out the window.

    I guess it has a bit of life left in it, but with the article talking about 'single molecule' focal points. I geuss we are about to run into a little wall if these ever actually make it to market.

    Of course, with the computational power that will come of this, maybe we will be satisfied for a while. Somebody once said "Nobody will need more than 640 k of RAM" Right?

    • "Well, there goes Moore's law out the window."

      Moore's Law [intel.com] describes an increase in transistor counts.

      I hope you are referring to the idea that traditional microprocessor design would be obsolteted by 'optical computing' thus halting the advancement of traditional microelectronics, thus stopping the advancement of transistor counts as opposed to somehow having transistors being used in 'optical computing.'

      • Moore's Law describes an increase in transistor counts.

        I hope you are referring to the idea that traditional microprocessor design would be obsolteted .....

        Well, yes.

        The role transistors play will not always be performed by transistors. Just like vacume tube technology halted in the 70's and buggy-whip disigns have been stagnate (for the most part) since the 1920's.

        But I think you missed part of my point. That being: weather of not you are talking about a transistor, once a single molecule is used as the focal point of a device, the count will not be rising much from there.

        Don't read too much into this. I am in my early 30's and for IT people my age, Moore's Law has been darned-near the only constant in our professional lives. I was just "thinking out loud" about the possibility if it now being obsolteted.

        kind of a bummer: But at least it will be around for at least a bit longer.

        • Man, that's an awful lot of typos for someone in their 30's !

          (vacuum, designs, stagnant, "whether or" "of it" obsolete)
        • "But I think you missed part of my point. That being: weather of not you are talking about a transistor, once a single molecule is used as the focal point of a device, the count will not be rising much from there."

          OK I get it ... and yes I did miss your point at first. Thank you.

    • Of course, with the computational power that will come of this, maybe we will be satisfied for a while. Somebody once said "Nobody will need more than 640 k of RAM" Right?

      I'm not saying that more power wouldn't have many uses, but it always bothers me when people quote the "640K" line about modern computers. Imagine if Bill Gates, living in three bedroom house, had said "Nobody needs more than three bedrooms." And then now, living in a forty bedroom house, he says "Nobody needs more than forty bedrooms."

      The latter, I think, rings a lot more true than the former. In most endeavors, diminishing returns can kick in after a while. It's the same reason we can't get away from the x86 architecture: There are more important issues than raw performance.
      • and not to mention that the "640k" quote often attributed to bill g is an urband legend [urbanlegends.com].
      • As I see it, there are two classes of problems: 1) problems for which there's some clever, efficient algorithm (like sorting and serching), i.e. essentially easy problems and 2) problems that are not easy, where the only known option is to try all the solutions and see which work. There is a great divide between these two classes of problems.

        Computers are now fast enough to do the easy problems comfortably, even on quite large datasets. These are the ones people have in mind when they say computers are "fast enough."

        But computers are no where near fast enough to solve large problems of the second kind, and it doesn't seem that they ever will be in the forseeable future. A problem of this type might be, "what lossless compression/decompression algorithm under 1000K in length has the highest average compression on a given sample dataset?" It's easy to write a program to solve this problem, but awfully hard to wait for it to finish.

        I think we're falling into the gap between easy and hard problems. We can do easy problems easily, but have no feasible way to approach the hard problems.

  • Learnt a new word.... (Score:3, Funny)

    by marko123 (131635) on Wednesday August 28 2002, @08:33AM (#4155736) Homepage
    I must have been out of the negative refractivity thread of modern physics, but I love this word...

    "They had free drinks that night. Trevor was absolutely PLASMONIC. I mean... shit, man! he almost had a negative refractive index. Lucky we got him in a taxi when we did"
  • Sounds like this technology could drastically improve implementing Quantum Cryptography. Imagine, long distance completely secure connections , that are provably unbreakable. Lets see Carnivore tackle that.

  • Some Claims are absurd (Score:3, Informative)

    by slashnot007 (576103) on Wednesday August 28 2002, @08:41AM (#4155776)
    Much of what is claimed in the article and comapnion article is wrong, no doubt distorted through the prism of some "science writer" or attempt to dumb it down. For exampe, you cant focus light to a perfect point or even less that the wavelength of light.
    the ways one can escape these limits in a semantic sense is that you can change the index of refration of the media so the wavelength is shorter than in vaccum, but that's not really accomnlishing the goal. Alternatively, near field or or ther diffraction effects can confine a light field to a region smaller the wavelength, but it cant propagate in vacuum/air that way.

    likewise the claim you could make a perfecly flat focusing lens by combining poistive and negative materials is pretty hilarious too. You can do that right now with conventional positive only materials. (example take two plano confave lenses of high index material, and fill the space between them with water. voila!).

    on the other hand you could do a lot of really interesting stuff with negative index materials that is harder to put in laymans terms. one example, the speed of light might be faster than in vacuum.

    • One interesting application of this might be zero reflectivity materials. Right now the problem with (almost) all materials is that if they have any absorption at all then by defineition thay have a different index of refraction than air and consequently an inescapable reflectivity. (yes, black paint always refelcts some light!). this is bad news if you are a stealth airplane. Some ferrite materials posses an unusualy perimtivity/permiability that lets them actually have absorption yet a matched index but they are too heavy to put on an airplane. this might break open a whole new class.

      • One interesting application of this might be zero reflectivity materials

        now how would that work anyway... if you painted a basketball with "zero reflectivity" paint, you would no longer see the ball, because no light would bounce from it to your eyes, but you would also not be able to see anything behind it... so what would you see.. .or perceive??

    • one example, the speed of light might be faster than in vacuum.

      No, the speed of light in the medium need only be faster than the speed of light in the surrounding medium--e.g. air.

    • What I find particularly absurd is the reliance on the existence of so-called "negative numbers." Puh-leez.
      • No need to get technical, but it is in fact possible to have qauntum probability waves exiting a resonator before the entered it. (No i'm not making this up, it was published in Nature two years ago.) There may be not infomation content is transmitted. Recently it has been proposed that gravity waves may be faster than electromagnetic waves (i.e. light).

        but in regards to the article, the final comment was sheer speculation. THe existence of a negative index suggests that it might be possible to create a composte substance with an index less than one yielding an electomagnetic propagation media with a speed faster than vacuum.

  • Negative R.I. for sure? (Score:1, Interesting)

    by Anonymous Coward
    Didn't we have a story [slashdot.org] about how skeptical [physicsweb.org] scientists were about these results.
  • I'm still waiting for the next big breakthrough in quantum computing, but this new optical technology will give way to some really fast stuff. Just imagine having a quantum computer cpu with optical connections to a solid-state hard drive. At least there is something to look forward to in computing nowadays.
  • Damn, that sounds cool!

    Plasmonic nanomaterials

    Plasmonic nanomaterials

    Plasmonic nanomaterials

    Now I'm sorry I went into software. I really, really wish I could tell people that I was into plasmonic nanomaterials.

  • Is it just me or does "surface plasmon polaritons" sound like somebody left the StarTrek technobabble generator on overnight?

    Actually way kuel stuff, SciAm had an article at length about this a few months back, and it was an awesome read... one of the other cool effects of this technology is optical microscopes that are orders of magnitude higher in resolution... visual systems that will let people look at things in optical frequecies that were limited to electron microscopy in the past (means we can see things way up close, that are still alive and kicking... or nanoscopic...)

    "The future's so bright you need shades..."
  • How stable is all this going to be? I have to believe this is only working in vacuum conditions at the moment. I doubt it's going to be hitting the inside of anyone's computer in the near future. As the article says, the first applications will probably be high power microscopes. Not too much else seems feasible in the near term.
  • I thought the index of refraction was defined as:

    n = (speed of light in vacuum)/(speed of light in medium),

    or n = c/cmed

    Now, convenctional wisdom and all modern science says c is always the bigger value, so n is always >= 1, but positive. How the heck does one get a negative refractivity? Niether of these quantities should be signed, let alone oppositely signed, right? What is meant by negative refractivity?

    Tim
    • It happens when the light goes backwards.... :-)

      cmed < 0
    • The use of the term "negative" regarding a material's refractive index is really semantic. Basically, as described by Snell's Law, light bends toward the surface normal as it crosses the boundary of a material. However, materials with a "negative" refractive index have the opposite effect: they cause the light to bend away from the surface normal.
    • I thought the index of refraction was defined as:

      n = (speed of light in vacuum)/(speed of light in medium),

      another definition, IIRC, is c/sqrt(mu*epsilon)

      mu = permeability
      epsilon = permittivity

      both are coeeficients of the linear response of meterials to the EM field.

      now, if the linear response of a material to EM fields is complex, I guess you can have negative (or imaginary) n.

      imaginary means exponential decay or growth, BTW, but of course in the case of growth the material stops responding linearly at some point, thus changing the dependance.

      IIAC, negative n does not really mean the speed of light reverses .

      Now, convenctional wisdom and all modern science says c is always the bigger value, so n is always >= 1

      AFAIK you're right in saying c is always the bigger value, however there exist superluminal photons [cerncourier.com] , which have phase velocity higher than c.

      This is not, again AFAIK, related to the response medium but to other quantum phenomenas.

      The universe can do some weird, convoluted vodoo ...
      • now, if the linear response of a material to EM fields is complex, I guess you can have negative (or imaginary) n.

        If n=c/sqrt(mu * epsilon) as you suggest, then negative n would simply result from the negative roots of the sqrt. No fancy gymnastics with complex roots necessary.

    • Your definitions are correct, but incomplete. The speed of light, c, (and cmed for that matter) are defined as c^2 = e*u (electric permittivity of the substance times the magnetic permeability of the substance). In other words, the speed of light is determined by how well the substance it is travelling through can be influenced by electric and magnetic fields.


      To complete the definition:


      n^2 = c^2/cmed^2 = (e0 * u0)/(e * u).


      (The zeroes indicate that they are in free space.)


      Now to the questions: Negative refractivity should be impossible. Both e and u are positive quantities, and if they weren't, the square would make them at the minimum postive imaginary numbers. The problem is that e and u are only scalars if you are working with the prefered direction of the substance. Otherwise, they are 2nd order tensors (3x3 matrices). (e0 and u0 are always scalars.) I am not sure how this would influence the outcome w/o doing the math. But, it may allow for this type of effect.



    • FYI: The real part of the refractive index for metals is, in general, less than 1.

  • Gheesh. I thought we had enought problems recycling our old CRT's. I wonder what kind of issues these materials are gonna have if they make it mainstream?

    I wonder what country we're gonna pollute this time. Oh! Bad American!
    • um... it seems they're made of metal. So, shouldn't be any more nasty to the environment than, say, a few bottle caps. Not that bottle caps are good for the environment, but wouldn't it be more effective to ban, say, styrofoam than plasmonic materials?

  • Oh, goody! (Score:3, Funny)

    by KC7GR (473279) on Wednesday August 28 2002, @09:29AM (#4156047) Homepage Journal
    Ha! New words to play with. Let's see here...

    'Surface plasmonic polaritrons...' Nah, too long. Let's condense it down to something like this...

    "Give your laundry that FRESH, SPARKLING, NEGATIVE REFRACTIVE INDEX with Maytag's NEW SURFACE PLASMONITRON!! Yes, you too can have your clothes looking like they got lost in a physics lab for a month, AND REVERSE THEIR POLARITY, all in three easy cycles!!!"

    (Read all warning labels before use. Not recommended for cashmere, poodle fur, or llama wool. Batteries most definitely NOT included, minor assembly and Ph.d required. This product is not available in Pakistan).

    Ok... who else wants to contribute? ;-)

  • It sounds cool and all, but what do you get with photon logic over electron logic?
    Is it faster? Cheaper? Less heat? More Compact? Some of these but not all of these? What do you lose by switching to photon?

    It does sound like good stuff, but what exactly is the good?

  • I figure the producers of Enterprise should be able to get five episodes worth of plot points out of the words "plasmonic" and "polariton."

    Stefan

  • Today on slashdot, we have a nanomaterial that focuses light backwards, and also a nanomaterial that can attach to a flat, clean, dry surface well enough to support 200 lbs with a few square inches (using forces thought to only have effects at microscopic scales). The former is found only in labs and is brand new, and the latter is found in gardens and is older than humanity.

    It's sort of interesting that the article refers to the negative refraction materials as "unnatural". Nature has been doing nanotech for millions of years now. It's pretty likely that, if these materials turn out to be good for anything that occurs in nature, they can be found there.
  • plasmonic nanomaterials
    Heck, that even sounds cool.

  • What negative refraction means (Score:3, Informative)

    by zero_offset (200586) on Wednesday August 28 2002, @01:35PM (#4158060) Homepage
    For those of you trying to figure out what "negative refraction" actually implies, the article at the URL below has a pretty easy-to-understand explanation of the key characteristics.

    03/2001 photonics.com article [photonics.com]

    • what this means is that u can bend the light BEYOND the normal. it is NOT reflecting off the surface of the material, but rather entering the material and reversing direction within it. (iMHO)

      • Kind of like a weiner, which typically has a positive index of refraction. But pull it back between your legs, and you've got negative index of refraction. If you've got a stiffy pointing towards the sky, that's reflection.
    • wouldn't that mean you would have to FORCE electrons through the material? that seems like a bad consequence.

      • NO, the surface plasmons they mention are a combination of an electromagnetic field (=light) with electrons that oscillate at the same frequency in the metal.


        These are perfectly legal solutions of Maxwell's equation and only occur on the surface (hence the name) of metals.

    • Re:Remember your physics (Score:2, Interesting)

      by Anonymous Coward
      It doesn't mean the velocity is faster than 'c'. It only means the light beam is deflected towards the opposite direction ( angle of refraction > 90 deg )
    • Negative refractive index does not mean light is moving faster than C. According to Snell's law the refractive index of any material with respect to vacuum = velocity of light in vacuum / velocity of light in material.

      So for dense thingies refractive index greater than 1. Eg glass. Now the refractive index of material A with respect to material B is Vel in B / Vel in A. So light travelling from Inside a glass slab to outside would think it encountered refractive index less than 1.

      Now negative refractive index mean negative velocity ?? I dunno. Refractive index can also be calculated from Sine (incidence angle) / Sine (refracted angle). The only way to get negative refractive index is if Refracted angle greater than 180. (Remember high school trigonometry. Sine is negative only in the third and fourth quadrant). Now refracted angle greater than 180 would mean that light has suffered total internal reflection. So a negative refractive index material would behave like a mirror and not a lens. (hence giving negative velocity - velocity is a vector, has magnitude as well as direction). I smell a rat in the article.

      -Dracken
    • Actually, light CAN move through objects faster than 'C'. Researchers have made light move over 300C!

      the story from CNN is here:

      http://www.cnn.com/2000/TECH/space/07/20/speed.of. light.ap/

    • If they can fiddle with light and directly manipulate it, does this mean they could possibly simulate some form of "invisibility". E.g. bending light completely around an object, so that the object no longer refracts light itself, but is essentially hidden within a sphere of redirected light?

      I suppose the current theory applies only to light within some conduit of sorts, like fibre optics, but it would be cool if it had other such uses


      I'm not a physacists, so feel free to critisize, but it's just a thought... direct manipulation of light could be a powerful thing.

      -Quote-
      "Using these plasmonic nanomaterials, we hope to directly manipulate light, guide it around corners with no losses and basically do all the fundamental operations we do with electronic circuits today, but with photons instead," said Shalaev.
      -EndQuote-
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