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Engineers Devise Invisibility Shield
GerritHoll points out an article in Nature according to which "researchers at the University of Pennsylvania 'say that a "plasmonic cover" could render objects "nearly invisible to an observer.' Earlier attempts at invisibility worked by colouring a screen to match its background, like a chameleon. The described technique is new, because it works by the concept of reducing light scattering. It is not a 'magic cloak,' however, because it will not work for the full range of visible light and needs to be adjusted precisely for the shape of the object. However, the concept could find an application in stealth technology."
What sort of armor class do you get with that?
I didn't see that one coming.
This technology would only work for microscopic objects (as they must be the same size as the wavelength of light hitting it), and only a single wavelength. So in other words, for you to get a nice, new cloak of invisibility you'll need to be microscopic in size and constantly in environments with only one wavelength of visible light hitting you. =)
Well, back to the drawing board.
-Vendal Thornheart
See, it hides my identity when I post on Slashdot!
From the article:
...it would be more like the shielding used by the Romulans in the Star Trek episode "Balance of Terror" in 1966, which hid their spaceships at the push of a button.
...it's called a "cloaking device", you insensitive clod!
Why do surgeons need an invisibility cloak? To hide from malpractice lawsuits?
The article puts two techniques next to eachother, as if it were alternatives for the same problem. This is false.
The proposed system with plasmonic covering reduces the scattering of light. The lightwaves pass by the object as were the object very small, smaller than it actually is. Hence it only works with objects that are allready very small, because otherwise the object would cast a shadow. (Light passes by, not through)
The system with light detectors and emitters mimics the scene that is behind (bigger) objects with respect to the viewer. You could actualy say that it fills in the shadow cast by the object.
So were the first system reduces the shadow effect, the second replaces the shadow alltogether. I could actualy see these two systems used along side eachother rather than instead of eachother.
the effect only works when the wavelength of the light being scattered is roughly the same size as the object
This would make it the perfect for those awkward moments when your nanobots are being attacked by lasers (mounted on sharks?)
The world has changed and we all have become metal men.
The Japanese "invisibility cloak" is nothing more than the front projection technique used in 2001: A SPACE ODYSSEY and many other films. That's like claiming that we have a super weapon that can hit an enemy anywhere -- provided he stands right here on this spot marked X. The alleged surgical and pilotting applications sound equally silly. It is an infinite regression of "if we can fit a camera in front of the surgeon's hands, we can project an image behind them to make a really cool effect that they are invisible!"
I don't think these engineers devised any sort of "invisibility shield"
Yeah, that's all basically correct. I did research on annealing these metal films to try to change their optical properties (we ran into some problems with grain structures in the metal growing during the annealing process).
Most scientifically literate people probably haven't heard of plasmons because they only form when the surface of a metal is milled with a regular array of nanostructures. In this case you have an array of holes on the scale of tens to hundreds of nanometers in diameter. When there's some such repeating nanoscale structure it changes the electron energetics so that the energy to frequency ratio is similar to that of the electromagnetic spectrum, at which point light can couple with the surface electrons and form these longitudinal surface waves (I'm not a physicist yet, so some of this may be a bit shakey).
As the parent said it's these waves that can then travel through the holes milled in the surface out onto the other side, where for some reason or another, they'll reemit the energy stored in them as light. It's pretty cool because they've done tests and the light doesn't just come out of the holes. It's as if the light passes straight through the metal film. Furthermore, they know the light's not simply passing through the film, because they've also measured it and found a very slight delay due to the formation, propagation, and reemission of the plasmons.
The story I heard about the discovery of this phenomenon is kind of amusing. Apparently an English speaking chemist wanted an array of micro wells for some polymer reaction, asked a Chinese chemist if he could do make one. The Chinese chemist thought he was crazy and said it would take six months. Due to the language barrier, the "you're crazy" bit didn't make it through, and six months later the English speaker picked it up looked through it, and said, hey, there's nothing here.
One use they're currently looking into is very specific optical filters which can be built for any wavelength. The grad student I worked with mentioned way down the line the possibility for essentially infinite resolution displays, although how that'd work isn't quite clear.