New invisibility cloak hides objects from human view

Jul 27, 2011

For the first time, scientists have devised an invisibility cloak material that hides objects from detection using light that is visible to humans. The new device is a leap forward in cloaking materials, according to a report in the ACS journal Nano Letters.

Xiang Zhang and colleagues note that invisibility cloaks, which route electromagnetic waves around an object to make it undetectable, "are still in their infancy." Most cloaks are made of materials that can only hide things using microwave or infrared waves, which are just below the threshold of human vision. To remedy this, the researchers built a reflective "carpet cloak" out of layers of and etched in a special pattern. The carpet cloak works by concealing an object under the layers, and bending light waves away from the bump that the object makes, so that the cloak appears flat and smooth like a normal mirror.

Although the study cloaked a microscopic object roughly the diameter of a , the device demonstrates that it may be "capable of cloaking any object underneath a reflective carpet layer. In contrast to the previous demonstrations that were limited to infrared light, this work makes actual invisibility for the light seen by the human eye possible," the scientists write.

Explore further: Crafting ultrathin color coatings: Physicists produce vivid optical effects—on paper

More information: Nano Lett., 2011, 11 (7), pp 2825–2828 DOI: 10.1021/nl201189z

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A_Paradox
5 / 5 (1) Jul 27, 2011
I couldn't give this article 5/5 because it is so lacking in detail. Besides which the touted device is falling short by about 2 orders of magnitude.

I would have thought that effective cloaking would involve significant trade-offs such that light traveling from a cloaking device in any particular direction would be only a small percentage of the light that hit the device on the other side and which would normally have gone straight to the observer's eye.
thales
5 / 5 (4) Jul 27, 2011
Besides which the touted device is falling short by about 2 orders of magnitude.


Agreed. On the bright side, I finally have a way to hide my secret red blood cell. Don't tell anyone!
ZeroDelta
not rated yet Jul 27, 2011
Well, it's pretty straight-forward metamaterial stuff.

From the paper: "The bump clearly distorts the wavefront, creating a lobed pattern. The cloak successfully reconstructs the wavefront so that the output is unperturbed."

"These devices have demonstrated cloaking in visible frequencies for a certain polarization of light
based on intrinsic anisotropy in the crystals."

"A two-dimensional (2D) quasi conformal mapping (QCM) technique can be employed to numerically minimize the anisotropy in the index profile which results from the optical transformation."

"silicon nitride waveguide on a low index nanoporous silicon oxide substrate; the nitride layer and the nanoporous oxide layer are 300 nm and 510 m thick, respectively. The hole pattern allows for index modulation by varying the solid
filling fraction. The holes vary in size from65 to 20 nm."
Gawad
5 / 5 (9) Jul 27, 2011
This is exciting! They've finally managed to make an microscopic object invisible to the human eye!

Hey. Wait a minute...!
that_guy
5 / 5 (2) Jul 27, 2011
I take issue with the title - "New invisibility cloak hides objects from human view"

A red blood cell is distinctly too small for a human to see...so it was never in human view to begin with.

But yeah, I understand that they now have figured out...again...how to hide things in the visible spectrum. Go back a few months, and you'll find an article where it was already done...
physics4sure
1 / 5 (2) Jul 27, 2011
that would help to get rid of terrorist ,if we could make cloak large enough to hide our soldiers,so that they could grad them and just kill them....it would help a lot
Vendicar_Decarian
2.6 / 5 (5) Jul 27, 2011
that would help get rid of Americans, if terrorists could make a cloak large enough to hide then they could grad American Invaders and just kill them... it would help a lot.
physics4sure
1 / 5 (2) Jul 28, 2011
it's on the makers how they safely preserve the blue print and first let the cloak be designed at macroscopic level...it ll take time...
Simonsez
not rated yet Jul 28, 2011
To think, just two years ago they said cloaking things in visible light was just plain impossible.
Dichotomy
not rated yet Jul 29, 2011
And another 2 years before that the BBC had an online special about an object about the sized of a post-it pad that would "cloak" when turned on because it caused the light waves to travel around it. It was pretty cool and was able to hide a lot more than a blood cell. The only problem with bending light waves around something is that if you're inside the cloaked area, you can't see out!
poof
not rated yet Jul 31, 2011
Wow, just think in a decade or two we'll have full scale cloaking and then ill not only have to deal with virtual thieves stealing my property without being detected, but real ones too! The world will truly be a better place as a result of this amazing technology.

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