David Kirkpatrick

August 11, 2008

Cloaking device becoming feasible?

From KurzweilAI.net — I’ve blogged on 3D cloaking devices before, very likely the previous KurzweilAI.net linked blog post from mid-May is an earlier report of this project. Both stories originate from UC Berkeley.

At any rate, here’s 3D cloaking part two:

Practical Cloaking Devices On The Horizon?
PhysOrg.com, Aug. 10, 2008University of California, Berkeley scientists have created a multilayered, “fishnet” metamaterial that unambiguously exhibits negative refractive index, allowing for invisibility in three dimensions for the first time, Nature magazine plans to report this week.

 
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Update — Here’s another take on this story, once again from PhysOrg. This time with pictures!

From the link:

Two breakthroughs in the development of metamaterials – composite materials with extraordinary capabilities to bend electromagnetic waves – are reported separately this week in the Aug. 13 advanced online issue of Nature, and in the Aug. 15 issue of Science.

Applications for a metamaterial entail altering how light normally behaves. In the case of invisibility cloaks or shields, the material would need to curve light waves completely around the object like a river flowing around a rock. For optical microscopes to discern individual, living viruses or DNA molecules, the resolution of the microscope must be smaller than the wavelength of light.

The common thread in such metamaterials is negative refraction. In contrast, all materials found in nature have a positive refractive index, a measure of how much electromagnetic waves are bent when moving from one medium to another.

In a classic illustration of how refraction works, the submerged part of a pole inserted into water will appear as if it is bent up towards the water’s surface. If water exhibited negative refraction, the submerged portion of the pole would instead appear to jut out from the water’s surface. Or, to give another example, a fish swimming underwater would instead appear to be moving in the air above the water’s surface

And here’s the image:

On the left is a schematic of the first 3-D "fishnet" metamaterial that can achieve a negative index of refraction at optical frequencies. On the right is a scanning electron microscope image of the fabricated structure, developed by UC Berkeley researchers. The alternating layers form small circuits that can bend light backwards. Image by Jason Valentine, UC Berkeley
On the left is a schematic of the first 3-D “fishnet” metamaterial that can achieve a negative index of refraction at optical frequencies. On the right is a scanning electron microscope image of the fabricated structure, developed by UC Berkeley researchers. The alternating layers form small circuits that can bend light backwards. Image by Jason Valentine, UC Berkeley

May 14, 2008

More science fiction turning into science fact

From KurzweilAI.net, taking steps toward an invisibility cloak

New material may be step towards 3D invisibility cloak
New Scientist, May 13, 2008

A researcher at the University of California at Berkeley claims to have made a 3D metamaterial with a negative refractive index, the first 3D material of this kind.

Physicists have in recent years made it possible to bend, or refract, light in the opposite direction to any natural materials. These metamaterials make it possible to create invisibility cloaks that hide an object by steering light around it. The materials and “invisibility cloaks” built so far have all been flat, working only in two dimensions.

The negative refraction index will have to be confirmed by measuring the speed of light in the material.

See Also Physicists draw up plans for real ‘cloaking device’

 
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