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## A Step Towards an Invisibility Cloak172

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

• #### Invisible to lasers, anyway. (Score:3, Interesting)

on Saturday April 07, 2007 @10:23PM (#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?
• #### Re:Invisible to lasers, anyway. (Score:5, Interesting)

on Saturday April 07, 2007 @10:37PM (#18652525)
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.
• #### One step towards the most duped story (Score:4, Interesting)

on Saturday April 07, 2007 @10:38PM (#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.
• #### Re:*yawn* (Score:2, Interesting)

<eviljedi120@optonline.net> on Saturday April 07, 2007 @10:54PM (#18652635)
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 could be in the corner watching!
• #### Re:Invisible to lasers, anyway. (Score:5, Interesting)

<Nospam DOT 01 DO ... veltman DOT org> on Sunday April 08, 2007 @12:16AM (#18653039) Homepage Journal
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.

Michael
• #### Problem with Invisibility Cloaks in General ... (Score:2, Interesting)

on Sunday April 08, 2007 @12:25AM (#18653095)
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.
• #### Re:Invisible to lasers, anyway. (Score:2, Interesting)

on Sunday April 08, 2007 @12:55AM (#18653247)
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 robust applications.
• #### Re:Serious Note: Foreign Students & Critical T (Score:3, Interesting)

on Sunday April 08, 2007 @01:07AM (#18653313) Homepage Journal
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/artic 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.
• #### Re:A little note about free speech (Score:3, Interesting)

on Sunday April 08, 2007 @01:48AM (#18653491)
While I agree that Slashdot shouldn't ban any exercise of free speech, I'm pretty sure one of this site's rules is no advertising your site in discussions, espeically if it has nothing to do with the discussion at hand. This guy is just spamming articles with ads, without making even the slightest effort to make it look like a normal response. I agree that there needs to be a "report abuse" link that /. higher-ups can then review and make a decision based on. There's a difference between free speech and system abuse.
• #### Re:Invisible to lasers, anyway. (Score:3, Interesting)

on Sunday April 08, 2007 @04:46AM (#18654045)
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 wavelengths at will. Or...other ways. Really, I don't see it being a problem, the researchers saying it could be "useful" are just be sensationalistic. Or perhaps they want military funding, which in my opinion is a waste because it seems incredibly unlikely that nanoscale invisibility armor will ever be practical.

(well, it might be SOMEDAY, but I suspect that era would be around the same era when machines do all the fighting, and we have different considerations.
• #### Dirt/damage resilience? (Score:3, Interesting)

on Sunday April 08, 2007 @06:40AM (#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.
• #### Re:Invisible to lasers, anyway. (Score:3, Interesting)

on Sunday April 08, 2007 @06:40AM (#18654383)
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 detecting enemy forces/missile silos from above. This is because equipment gives off heat even if it is dark/concealed.

I have not RTFA and do not know what "one wavelength" means.

• #### Re:Invisible to lasers, anyway. (Score:2, Interesting)

on Sunday April 08, 2007 @07:43AM (#18654591) Homepage
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.

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