Plan For Cloaking Device Unveiled

Robotron23 writes "The BBC is reporting that a plan for a cloaking device has been unveiled. The design is pioneered by Professor Sir John Pendry's team of scientists from the US and Britain. Proof of the ability of his invention could be ready in just 18 months time using radar testing. The method revolves around certain materials making light "flow" around the given object like water."

Re:Nonsense -- water does not look like light.

[Salsaman]

A little further down, they say:

"What you're trying to do is guide light around an object, but the art is to bend it such that it leaves the object in precisely the same way that it initially hits it. You have the illusion that there is nothing there"

Re:maths?

[patio11]

Yes, in UK and Australia (and probably other Commonwealth nations, although I don't have personal experience outside of those two -- Canada I think follows American usage) "mathematics" always shortens to "maths" when describing a field of study ("My worst subject at uni was maths"), the process of computation ("Help me, I can't get the maths to work out here"), etc etc.

Research abstracts

[FleaPlus]

The BBC article mentions a couple of articles in the current issue of Science. Here's the text from their research abstracts:

Controlling Electromagnetic Fields [sciencemag.org]
J. B. Pendry, D. Schurig, D. R. Smith

Using the freedom of design that metamaterials provide, we show how electromagnetic fields can be redirected at will and propose a design strategy. The conserved fields--electric displacement field D, magnetic induction field B, and Poynting vector S--are all displaced in a consistent manner. A simple illustration is given of the cloaking of a proscribed volume of space to exclude completely all electromagnetic fields. Our work has relevance to exotic lens design and to the cloaking of objects from electromagnetic fields.

Optical Conformal Mapping [sciencemag.org]
Ulf Leonhardt

An invisibility device should guide light around an object as if nothing were there, regardless of where the light comes from. Ideal invisibility devices are impossible due to the wave nature of light. This paper develops a general recipe for the design of media that create perfect invisibility within the accuracy of geometrical optics. The imperfections of invisibility can be made arbitrarily small to hide objects that are much larger than the wavelength. Using modern metamaterials, practical demonstrations of such devices may be possible. The method developed here can be also applied to escape detection by other electromagnetic waves or sound.

Unfortunately, I don't seem to have access to the full papers.

Re:Metamaterials

[emurphy42]

No. [wikipedia.org]

Uggggghhhhhhh!!!!!

[Anonymous Coward]

For the ignorant among you there is a BIG (as in several orders of magnitude) difference between Radar EM waves and light. Dudes and dudettes if you going to post about a scientific article how about reading up on the science behind the article so that you can post intelligently?

ac

Re:maths?

[Mant]

In American English it's Math, but in British English (as used by the BBC) it's Maths.

Nano-engineering?

[sanman2]

Various articles point out that the lensing structures bending the light have to be smaller than the light's wavelength. That means for visible light spectrum, which is around 400-700nm, your meta-material structures have to be molecular-sized. This is much smaller than what's required for radio or microwaves, which are centimeters to meters in length.

So either you'll have to nano-engineer your cloaking shell from the molecular level, or else you'd have to find a way to convert the light that strikes it into a lower frequency (higher wavelength) that you can handle more easily. If you had some super-efficient down-converter/up-converter material coating the surface of your cloak, this might then enable you to bend the light without having to go all the way down to nanometer size for your meta-material lensing structures in the cloaking material itself.

I can imagine the color green would be particularly useful to cloak against, because that would allow you to be invisible in front of vegetation/greenery.

Re:Nonsense -- water does not look like light.

[bw_bur]

I don't think you've RTFA. You certainly haven't read the paper.

At best, this would provide almost perfect camouflage. Bits of colour from the background would not show up on you; from whatever direction you look at it, you would see right through it. The light goes around the cloaked object, but there is no way for you to know that.

Of course, this only works over a restricted frequency range. In addition, since these metamaterials are usually based on resonant systems and are consequently strongly dispersive, there is some initial scattering while the resonance is established; very short pulses defeat the invisibility.