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A Step Towards an Invisibility Cloak 172

An anonymous reader alerts us to work out of Purdue University in Indiana, where researchers have produced a design for a method of cloaking objects of any shape and size at a single wavelength of visible light. The math for such an invisibility effect was worked out last year at Duke and in the UK, but the new work, to be published in Nature Photonics this month, is the first practical design. The lead researcher, Vladimir Shalaev, notes that even though the current design works only at a single wavelength, and so would not convey true invisibility, it could still be useful — against, for example, night-vision goggles or laser target designators. Shalaev calls the technical challenge of producing an all-wavelengths cloak "doable in principle."
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A Step Towards an Invisibility Cloak

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  • by Anonymous Coward
    After mass production and commoditization, we will have invisibility T-shirts, invisibility sandals, and invisibility shorts.
  • by FooAtWFU ( 699187 ) on Saturday April 07, 2007 @11:22PM (#18652421) Homepage
    Never has this notice been more appropriate:

    Nothing for you to see here. Please move along.
    • by vxd ( 798177 )
      Let me know when it's available for visible light so I can go watch Pamela Anderson have sex live.
      • Re: (Score:2, Interesting)

        Yes, just what our society needs. So we get these "invisibility cloaks" and what is next? Use in law enforcement? Cops can spy on us from behind these cloaks? An amendment to the Patriot Act? I'm not saying these are necessarily bad things, but we sure as hell have to weigh the possible negative uses of such a technology.

        Following suit with that article about the RIAA pushing for pretexting in California, I could just see them getting their hands on invisibility cloaks.
        Be careful pirating music, the RIAA c
        • Re:*yawn* (Score:5, Funny)

          by BakaHoushi ( 786009 ) <Goss.Sean@gmaiNETBSDl.com minus bsd> on Sunday April 08, 2007 @04:20AM (#18653787) Homepage
          Don't worry. We have the technology to prevent such abuse. Simply place an upside down basket on a stick, and place a dollar bill under it. If a record executive or a lawyer is hidden in a corner, they won't be able to resist and the basket will fall on them.
        • Actually,

          If someone could spy on you from within the cloak, it would no longer be invisible, since he would have to absorb photons coming from the object he's observing, instead of passing them through.

          this in turn would make him look like a "dark" spot instead of invisible.

          • by cnettel ( 836611 )
            True, but practically we can think about something that lets 0.001 % or so of the light through. In daylight, that should be enough for the observer inside to still see what's going on (the range of usable eyesight is quite astounding), while it might be limited enough to still be hard to detect for those on the outside. (Hint, though: don't use a flashlight while you're wearing the cloak in a very dark room.)
    • Re: (Score:2, Funny)

      by aldo.gs ( 985038 )
      Nothing for you to see in this wavelength. Please select another one.
    • The main article mentions that this cloaking technology has military applications. Given the sensitive nature of this technology, should we prohibit certain foreign students from working on research projects exploring cloaking technology?

      In the late eighties, the University of Michigan at Ann Arbor prohibited certain foreign students from participating in government-funded research related to VLSI circuits. At the time, various alarmists in Washington warned that Japan would soon eclipse the USA in high

      • Re: (Score:1, Funny)

        by Anonymous Coward

      • Re: (Score:3, Interesting)

        by cyphercell ( 843398 )
        If we don't let Japan and China learn about the technology, who will build it? All joking aside, countermeasures already exist and in many cases are far more advanced. Either way India is not considered an enemy http://www.washingtonpost.com/wp-dyn/content/arti c le/2006/04/19/AR2006041902480.html [washingtonpost.com]. If you're concerned about outsourcing, don't be, let the Indians go to school in the US, that way at least our universities don't rot from lack of use.
        • who needs to develop more countermeasures? Mobile phone transmitters could be used, just search for the blank area...
      • by kalidasa ( 577403 ) on Sunday April 08, 2007 @09:24AM (#18654773) Journal

        There's nothing in this article to suggest that the student with the Indian name (Uday K. Chettiar) is not an American citizen, nor that Wenshan Cai or Alexander V. Kildishev are not American citizens, or that Vladimir Shalaev himself is not a US citizen (the fact that he was educated in Russia isn't an impediment: my grandparents were educated in England, and became citizens as adults); a cursory Google search finds nothing to suggest that they are not US citizens, either. However, I do know that Title 22 of the US code includes International Traffic in Arms Regulations (http://www.epic.org/crypto/export_controls/itar.h tml), and that universities and private companies in the US are required to stick to these regulations pretty closely, for fear of losing all federal funding: technologies that are covered under these regulations can only be worked on by US Citizens and those with "permanent resident" (green card) status. The fact that there have been a number of prosecutions of companies for technology transfers to China is proof that these regulations are taken seriously (though one does wonder about equality of enforcement with this particular administration).

        So, apparently you assume that anyone without a European name is not a citizen - or, at least, anyone with an Indian name is not a citizen: you didn't question Prof. Shalaev, Mr. Cai, or Mr. Kildishev. Looking at your website (http://www.geocities.com/deskofreporter/), I see that you do raise some interesting points about Taiwan's relationship with China, but that the tone you use in doing so has an aroma of xenophobia. I'd suggest that you look into the history of great American immigrant patriots, beginning with Alexander Hamilton and continuing on through Albert Einstein (he became an American citizen in 1940 and remained one until his death).

        • by kmac06 ( 608921 )
          I'd suggest that you look at the make up of any engineering or physics grad school in this country. At most, it's 50% American students. The assumption that these students with foreign-sounding names are foreign is a very safe one. Now I do think the GP is being alarmist, and that the potential military uses of this technology is so far off that restricting work on this based on citizenship is absurd.
      • by h4rm0ny ( 722443 ) on Sunday April 08, 2007 @09:56AM (#18654885) Journal

        Out of curiousity, what comment would you make about Japan or China excluding US scientists access to this research? Would you object? Because the way things are going, the US is going to be increasingly finding itself in the position of other countries having a lead in certain technological areas.

        As to India not signing up to the NPT, that would carry a little more moral weight if the US wasn't ignoring the treaty itself.

        And Iranian students seeking bombs, is that a particular problem at your university?
        • The US blows hot and cold on practically all treaties, depending on who is in the White House. That doesn't excuse India from it's behavior regarding proliferation. The problem here isn't whether foreign scientists should be excluded from certain kinds of work - they *should*, and they *are*, under the terms of ITAR, unless they have made the commitment of obtaining permanent residence status. The problem is the assumption that all of these folks are "foreigners." Just because someone has non-Anglo-Saxon n

    • by morcego ( 260031 )
      Gives a whole new meaning to the phrase "just because I'm paranoid, doesn't mean no one is watching me", hum ?
  • by AJWM ( 19027 ) on Saturday April 07, 2007 @11:23PM (#18652439) Homepage
    One wavelength hardly invisibility makes, but as the blurb suggests, it renders the target invisible to laser designators. Wonder how much power it can handle, would it be an effective shield against weapons-grade lasers?
    • by Opportunist ( 166417 ) on Saturday April 07, 2007 @11:30PM (#18652485)
      Weapons-grade lasers (i.e. lasers that do damage themselves) are with todays technology not really an issue. To create damage comparable to conventional methods of kaboom, you'd have to haul around a LOT more material and those pieces also tend to be a LOT more expensive. War is a cost/gain game, so don't expect to see any laser weapons too soon on the battlefields of the world.

      What this aims at is laser targeting systems. Those lasers carry hardly enough firepower to cause any damage (ok, should you look RIGHT into them, maybe you might have some problem), but they point out the target to a laser guided weapon. And, well, you can't hit what you can't see (unless you decide to fire a spray of those kickass expensive laser guided weapons, which has not really a good cost/gain relation).
      • by Kandenshi ( 832555 ) on Saturday April 07, 2007 @11:37PM (#18652525)
        I'm curious about something though...
        I have absolutely no experience/knowledge of these laser targetters, but how much more expensive would it be to be able to use different wavelengths of light?

        1. Try wavelength X: Oh darn, they're protecting against that with a shiny cloaking device, so...
        2. Try wavelength Y: Profit!!!/explosions

        The bomb or whathaveyou is searching for a very specific wavelength(X) right? But still doesn't seem like it should be impossible to program it to cycle through 2-3 wavelengths(X->Y->Z) until it finds your dot to lock onto.

        Still, it's a neat toy they're working on. I wouldn't mind one once they build one that's less selective.
        • I'm no expert for military grade lasers myself, but as far as I know, you need different media for different wavelengths. I.e. you'd have to mount one laser per wavelenth you want to try.
          • Re: (Score:3, Interesting)

            by ShooterNeo ( 555040 )
            Well, yes, that is true for most convential lasers. Usually, the light emitted is a property of what elements you dope the lasing medium with (for solid state lasers) or what gases you used (for well, gas lasers)

            However, if this horribly complex and expensive sound cloaking technology (against just 1 wavelength) ever become a threat, it would be trivial to upgrade the military lasers to a tunable one. There are numerous ways, including using free electron lasers which can be tuned to a wide range of wavel
            • So you can't just pop a colored lens in front of the beam? That's no fun.
              • Sarcasm, I hope. A colored lens blocks all frequencies except for the ones it allows through (hence the 'color'. A red one lets through red, ect)

                A laser beam obviously is only one frequency, so a colored lens does nothing for you. No light at all would get through.
        • Russian Dolls (Score:2, Insightful)

          by Nazlfrag ( 1035012 )
          To combat against multiple frequencies, you could place the cloak for X inside the cloak for Y inside the cloak for Z. Extending this way to full spectrum would be impractical, but multiple frequencies could more easily be blocked.
        • by hazee ( 728152 )
          One strategy might be to only turn on the device after the bomb or whatever is on its way.

          If you just switched it on at the last moment and then moved your tank, that might work.

          You'd be given advance notice that something was inbound by the fact that you were being illuminated in the first place.
          • Well, the tactic of "last moment" works for the attacker too. The AGM-114 [wikipedia.org] can be used that way. Fired indirectly without a target, it first of all climbs to altitude, then starts diving down. You can start the painting fairly late, usually too late for a human operator to react, activate defensive devices and evade it.
        • Re: (Score:2, Interesting)

          I'm in the armed forces, and we use NVG's( you call them Night vision goggles), there are no set wave lengths, the NVG'S either run passive which is the normal green night vision you see and infrared, which is intensified for a brighter image, given those different modes I assume have different wavelengths, but I wouldn't know the scientific terminology behind either.
          • by imkonen ( 580619 )
            I doubt this cloaking device is an issue for NVG's: You might only see one color when you look into the NVG, but that's just because that's the wavelength of the output resulting from the phosphor screen. I can't imagine any reason why the acceptable input wavelengths for NVG's would be limited to a single wavelength (or more realistically a narrow wavelength range): it's generally harder to make devices sensitive to a narrow range of wavelengths, and there'd be little to no advantage in doing so...you wo
      • "Weapons-grade lasers (i.e. lasers that do damage themselves) are with todays technology not really an issue. To create damage comparable to conventional methods of kaboom, you'd have to haul around a LOT more material and those pieces also tend to be a LOT more expensive. War is a cost/gain game, so don't expect to see any laser weapons too soon on the battlefields of the world."

        I didn't RTFA (hey, this is slashdot) but from the summary it sounds like a truly effective cloak of this sort is still some t
        • I can reassure you that military R&D is just like civil R&D: If there's no immediate application, your chance for funding is low.
      • by iamacat ( 583406 )
        You are forgetting the fact that, unlike kaboom, laser travels instantly (unless you try to shoot Martians) and precisely. This makes them better suited for shooting down airplanes and cruise missiles. There is also an option of using a smaller laser to blind the pilot.
        • Lasers also have a very big problem: No indirect firing, no ballistic arc. I.e. you want to see your target, which in turn means your target can see you. Even though lasers travel instantly, large lasers with a few megawatt of power need horribly long to charge (or, in case of gas emission lasers, are horribly expensive to fire and also quite hazardous to be near, i.e. only suited for ground based sites that can be left unmanned). Some branch of the US military (forgot which one) actually had a project runn
          • by iamacat ( 583406 )
            Especially that last part doesn't fit into the doctrine of high mobility of the US military. Not to mention that there are less expensive and more reliable means of getting rid of missiles.

            For example? I hear Patriot Intercepter missiles and space umbrella program didn't ever shoot anything down except under test conditions. If people are shooting nukes at you, maybe those very poisonous gases and expenses are not that bad after all.
            • And who might that be who's shooting nukes at me? The Soviet Union doesn't exist anymore and ... well, knowing some of their rocket systems I wouldn't be too scared. China has the potential, but is too busy getting cozy with the world trade system to want that relations to shatter. And beyond that the air gets thin, not because some country doesn't have "the" bomb (or claims to have it, or whatever), but having the bomb means jack if you can't deliver it.

              And UPS doesn't. I checked.

              So personally my fear of n
    • Re: (Score:3, Funny)

      Well, I guess this means we now have an effective anti-shark defense system...
      • Re: (Score:3, Funny)

        by Hal_Porter ( 817932 )
        The S1A1 remote controlled great white shark [newscientisttech.com] has a secondary offensive capability based on 1) rows of sharp teeth and 2) neural implant boosted hunger, all guided by a keen sense of smell. Obviously, we planned for Chinese frogmen in invisibility suits.

        This is all classified info BTW, please kill yourself after reading it, unless you happen to have SPECOPS/JAWS clearance.
    • by cyphercell ( 843398 ) on Sunday April 08, 2007 @12:10AM (#18652713) Homepage Journal
      I remember watching Black Hawk Down, and noticing that this troop (a motley crew of special forces) had the benefit of night vision effectively throughout the movie. When watching it I thoroughly believed that this was an advantage that made them successful in surviving the event. Imagine to armies fighting with night vision while one side has their special forces being cloaked.
      • by YGingras ( 605709 ) <ygingras@ygingras.net> on Sunday April 08, 2007 @01:33AM (#18653145) Homepage
        Except that night vision devices aren't restricted to a single wavelength. Night goggles only amplify the light in the whole spectrum. The whole thing, not a single wavelength. The output is converted to monochrome to stimulate the more sensitive rod cells. By limiting color output the pupil stays more dilated and can gather more light. Its the same thing with astronomical telescopes. You read your maps with a red light and you get eyes pieces with exit pupil [wikipedia.org] matching your night time pupil diameter.
        • Re: (Score:2, Interesting)

          by ozydingo ( 922211 )
          Even if night vision did work on detecting a single frequency, it wouldn't be a robust viable solution. Simply change the wavelength your night vision operates on, and the cloaking devices become useless. For this reason this technology as it stands currently is really not a viable solution for any military application as long as your opponents know anything about it (better hope they don't read Slashdot!)

          Don't get me wrong, I think it's still cool and a good first step, just not with any militarily robus
          • Re: (Score:3, Insightful)

            by rtb61 ( 674572 )
            The cloaking device is most likely just a spectrum shifting coating. Catch is, a dirty tank, would be a dead tank.
          • Of course they read slashdot. But don't be afraid, because, as every other slashdot reader, it's every unlikely they ever read TFA.
        • So if the cloaking worked out to say 95% then night vision goggles could probably be used as a countermeasure? If so, how well do you think it might work (I'm guessing 100%)?
        • Re: (Score:3, Interesting)

          by Plutonite ( 999141 )
          Yes, but infra-red sensors (which are one kind of night vision devices) typical use a tight range of wavelengths and thus could possibly be fooled or at least made inefficient. I do not know the extent of usage by the military in combat, but they tend to be useful in situations where you want to know if somebody is inside a room..etc before entering, because IR can penetrate thin barriers (doors..etc). As for air/space surveilance of ground activity, IR is far more important than light amplification in dete
    • by Anonymous Coward
      If it renders lasers less effective as weapons, then the natural result is development of multi-spectrum Phasers. You heard it hear folks! The cloaking device came first!

      Frickin Romulans.
    • One wavelength hardly invisibility makes, but as the blurb suggests, it renders the target invisible to laser designators.

      Invisible to laser speed checks would have some non military applications.

  • Happy Harry (Score:1, Funny)

    by jcarkeys ( 925469 )
    Harry Potter sits in the corner of the lab in his cloak snickering while the research scientists are excited to get one wavelength invisible.
    • Re: (Score:1, Insightful)

      by Anonymous Coward
      You do know Harry Potter is a fictional character, right?
  • That's what's gonna dictate whether it will be seen on the battlefield or not. If it's cheaper to produce another gunship or tank than to stealth an existing one, it will probably only be used on first strike weapons.
    • by Kijori ( 897770 )

      That's what's gonna dictate whether it will be seen on the battlefield or not. If it's cheaper to produce another gunship or tank than to stealth an existing one, it will probably only be used on first strike weapons.

      Fortunately, this isn't meant to be seen on the battlefield at all.

  • by noidentity ( 188756 ) on Saturday April 07, 2007 @11:38PM (#18652531)
    Sure, each article is a slightly different take, but I swear there have been at least four previous articles about some kind of invisibility device in the past year, all turning out to really be invisibility in a very restricted sense, i.e. a particular electronic device doesn't "see" the object.
    • Are you telling me you have the foresight to see more of these coming? Isn't that blindingly obvious? I wish I had that kind of vision. I have yet to see an invisibility device myself, FWIW.
    • Don't worry I take there's an upcoming post on a research group's article that claims invisibility when the viewer closes their eyes. While also not true invisibility the technique does work with all light spectrums. The researchers aren't suggesting a method to get the enemy to close their eyes but they do point out that everything has a downside.
      • by Grave ( 8234 )
        Oh, it's easy to get the enemy to close their eyes. Just get set their Slashdot comment filter to only show trolls.
      • by zCyl ( 14362 )

        Don't worry I take there's an upcoming post on a research group's article that claims invisibility when the viewer closes their eyes.

        This has been done. [wikipedia.org]
    • by e4g4 ( 533831 )
      It certainly is - strangley enough, I just finished reading an article [sciam.com] in this month's scientific american that describes the research mentioned in TFA done by John Pendry regarding an area of study called "plasmonics". Odd that TFA didn't mention the field, as it has applications that are far more realistic in the shorter term than cloaking devices, such as circuits that can convert electromagnetic energy at a given frequency and wavelength to an electron density wave that is the same frequency of the ligh
  • Meh (Score:4, Funny)

    by vertigoCiel ( 1070374 ) on Saturday April 07, 2007 @11:42PM (#18652571)
    Wake me up when you've got an "invisibility" device that'll let me sneak into the girls locker room without getting seen.
    • Your so-called 'invisibility device' is commonly known as a $50 at a strip club.
    • Re:Meh (Score:5, Funny)

      by Anonymous Coward on Sunday April 08, 2007 @12:50AM (#18652923)
      I think I have one, I've been invisible to girls for years.
    • Light can usually go along a path in either direction. If light isn't getting from you to the outside world. If the 'invisibility cloak' is a type of Luneborg lens with phonotonics materials to get the high refractive incides needed to get light to avoid the bit in the middle - the sort of thing in this month's 'Scientific American' - then yo will seem to be at the centre of a shiny ball. Kinda interesting to know how you would decide when all the bad guys had gone away, and it was save to take a peek out.
  • by unchiujar ( 1030510 ) on Sunday April 08, 2007 @12:15AM (#18652727)
    Oh noes, invisible sharks with lasers !!!
    • Re: (Score:1, Funny)

      by Anonymous Coward
      -I am sorry sir, we couldnt get sharks.
      -What do we have?
      -Sea Bass
      -Right, Are they invisible?
      -Only to one wavelenght
      -Oh well, that's a start.
  • by Anonymous Coward
    A friendly note to the photonics project managers, researchers and general staff:

    Don't make the same mistake I did. Learn from my experience that one should never, ever put the invisibility generator on top of the anti-gravity device.
  • Oh no! (Score:3, Funny)

    by Mikachu ( 972457 ) <burke...jeremiahj@@@gmail...com> on Sunday April 08, 2007 @12:31AM (#18652819) Homepage
    It's Denton. Remember the briefing.

    Don't mod me down just because you don't get it. ;)
  • Nothing to see here, move along.
  • Spock: Invisibility is theoretically possible, Captain--selectively bending light. But the power cost is enormous. They may have solved that.
  • What about the ground? Can the light even bend around an object that is stuck to another? I don't think so ...
    So wouldn't it make two dark spots on the ground? that could be used to identify if someone is using an invisibility cloak.
  • by OldManAndTheC++ ( 723450 ) on Sunday April 08, 2007 @01:27AM (#18653107)

    According to TFA:

    Leonhardt, a professor of theoretical physics, wrote a commentary piece about the Purdue paper appearing in the same issue of Nature Photonics. In the commentary, he compares the Purdue design to the Roman creation of "the first optical metamaterial," a type of glass containing nanometer-scale particles of gold. In ordinary daylight, a cup made of the glass appeared green, but then it glowed ruby when illuminated from the inside.

    So basically, this will be made out of (a form of) gold, and encircle the object to be rendered invisible?

    I'm betting that, in order to work, it will need to be inscribed with the phrase: Ash nazg durbatulûk, ash nazg gimbatul, ash nazg thrakatulûk, agh burzum-ishi krimpatul.

  • first off, theyre slowly replacing aging nvg's with FLIR systems, second nvg's sensed a spectrum, though i forgot which one, ultraviolet was it?, the point is its not a single wavelength... even if i'm wrong and it is only one wavelength then it would be trivial to broaden the spectrum or have the sensors modulate.

    the same thing with a laser, you modulate the beam according to a hash function for each laser/missile pair, the string that produces the hash code could easily be communicated real time from air
    • by hazee ( 728152 )
      Not quite sure what you mean about modulating a laser beam. Presumably you can switch it on and off in whatever fancy scheme you like, but it's going to remain the same wavelength. As others have mentioned, wouldn't you need different lasers to get different wavelengths? I seem to recall that dye lasers shift the output from one frequency to another, but not sure how practical this would be in a battlefield.

      Also, as regards communications between planes and ground troops - presumably planes want to minimise
  • Lightbending 101 (Score:2, Informative)

    This innovation and others like it have seen far too much press already. I know, I know, it's slashdot and no one RTFA anyway, but if you did you'd quickly realize that there really is nothing to see here. Let me explain at least for those of you who will read a comment if not any of the articles appearing in popular science sources for the last several months:

    Imagine for the moment placing an object behind a mirror. Better yet, inside a mirror. Amazing! You cloaked it from observation from visible wavel

  • I assume that if you wear one of these then you see nothing from 'outside' at that particular shade of red.

    So if they succeed in making one that works at all wavelengths of visible light - one could not see out. However: imperfections would let some light leak in, but the direction that it came from might be distorted and so give a very blurred view of the rest of the world.

  • by Jesus_666 ( 702802 ) on Sunday April 08, 2007 @07:40AM (#18654381)
    I'm not really into nanostructures, but this sounds pretty fragile. Someone has already pointed out that mere dirt could render it useless - but what about damage? Military vehicles aren't exactly going to be dusted off with badger hair brushes, so if the nanostructure is eroded by water (and cleaning brushes) the coat isn't going to last long. And if water can't do it small stones probably can and there are lots of those in the field.

    I see this as a general problem with light-bending nanomaterials - while they might work in a lab environment, real-world environments have enough ways of disrupting them to make them much less useful.
  • Goodness, I think I've read how many articles about this in the past couple of years? Six? Ten? They all have little glitches, like only working from one point of view, or only at one wavelength (frequently not a visible wavelength), or being pure simulations that have not even been tried in the laboratory yet. Many of them don't sound like "cloaks" at all, but like huge physical plants of machinery surrounding the object to be "cloaked."

    But they're all "promising" and they all "take a step toward" somethin

I've noticed several design suggestions in your code.