Author Topic: Metamaterials: a real invisibility cloak  (Read 10915 times)

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Offline Thucydides

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Re: Metamaterials: a real invisibility cloak
« Reply #50 on: January 26, 2012, 16:51:46 »
Further advances in cloaking technologies:

http://iopscience.iop.org/1367-2630/14/1/013054/pdf/1367-2630_14_1_013054.pdf

http://nextbigfuture.com/2012/01/experimental-verification-of-three.html

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Three-dimensional plasmonic cloak hides a cylinder from microwaves
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 New Journal of Physics - Experimental verification of three-dimensional plasmonic cloaking in free-space (14 pages) They optimized the cloak design for the 3 GHz range. They have hidden a cylinder from microwaves, demonstrating cloaking of an object in free space, rather than a two-dimensional image. The group has not been able to scatter visible light, but it expects that cloaking small objects is possible. The results pave the way to realistic, practical applications of 3D stand-alone cloaks for radar evasion and non-invasive radio frequency probing.

BBC News - The approach used is unlikely to work at the visible light part of the spectrum. Prof Alu explained that the approach could be applied to the tips of scanning microscopes - the most high-resolution microscopes science has - to yield an improved view of even smaller wavelengths of light.

In future applications, plasmonic materials could be combined with the structured metamaterials idea already in development elsewhere. Light can be channelled where it needs to go, or its effects undone, as need be.

Prof Apu said that if he had to bet in five years what kind of cloaking technique might be used for applications, for practical purposes, then he would say plasmonic cloaking is a good bet.

We report the experimental verification of metamaterial cloaking for a 3D object in free space. We apply the plasmonic cloaking technique, based on scattering cancellation, to suppress microwave scattering from a finite-length dielectric cylinder. We verify that scattering suppression is obtained all around the object in the near- and far-field and for different incidence angles, validating our measurements with analytical results and full-wave simulations. Our nearfield and far-field measurements confirm that realistic and robust plasmonic metamaterial cloaks may be realized for elongated 3D objects with moderate transverse cross-section at microwave frequencies.
Dagny, this is not a battle over material goods. It's a moral crisis, the greatest the world has ever faced and the last. Our age is the climax of centuries of evil. We must put an end to it, once and for all, or perish - we, the men of the mind. It was our own guilt. We produced the wealth of the world - but we let our enemies write its moral code.

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Re: Metamaterials: a real invisibility cloak
« Reply #51 on: January 26, 2012, 16:58:31 »
All the invisibility posts are now here, merged.

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Re: Could this have serious military aplication... Invisibility?
« Reply #52 on: January 27, 2012, 07:21:05 »
Bah, that's nothing, I have known several Gunners and Bombadiers that perfected vanishing to an art form, You would see them in the morning and then at the end of the day.
Same for some officers.
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Offline cupper

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Re: Metamaterials: a real invisibility cloak
« Reply #53 on: January 27, 2012, 19:54:07 »
All the invisibility posts are now here, merged.

Milnet.ca Staff

If they are invisible, how are we going to read them? ;)
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Offline Thucydides

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Re: Metamaterials: a real invisibility cloak
« Reply #54 on: February 23, 2012, 19:25:49 »
Low cost metamaterials are within reach. Once it becomes practical to make this in bulk many exciting possibilities open up:

http://oregonstate.edu/ua/ncs/archives/2012/feb/discovery-opens-avenue-“negative-refraction”-new-products-and-industries

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“NEGATIVE REFRACTION” OPENS AVENUE TO NEW PRODUCTS AND INDUSTRIES

CORVALLIS, Ore. – Researchers at Oregon State University have discovered a way to make a low-cost material that might accomplish negative refraction of light and other radiation – a goal first theorized in 1861 by a giant of science, Scottish physicist James Maxwell, that has still eluded wide practical use.

Other materials can do this but they are based on costly, complex crystalline materials. A low-cost way that yields the same result will have extraordinary possibilities, experts say – ranging from a “super lens” to energy harvesting, machine vision or “stealth” coatings for seeming invisibility.

Entire new products and industries could be possible. The findings have just been published and a patent has been applied for on the technology.

The new approach uses ultra-thin, ultra-smooth, all-amorphous laminates, essentially a layered glass that has no crystal structure. It is, the researchers say, a “very high-tech sandwich.”

The goal is to make radiation bend opposite to the way it does when passing through any naturally occurring material. This is possible in theory, as Maxwell penciled out during the American Civil War. In reality, it’s been pretty difficult to do.

“To accomplish the task of negative refraction, these metamaterials have to be absolutely perfect, just flawless,” said Bill Cowell, a doctoral candidate in the OSU School of Electrical Engineering and Computer Science. “Everyone thought the only way to do that was with perfectly crystalline materials, which are quite expensive to produce and aren’t very practical for large-area commercial application.

“We now know these materials may not need to be that exotic.”

The new study has explained how easy-to-produce laminate materials, created with technology similar to that used to produce a flat panel television, should work for this purpose. The findings outline the component materials and the theoretical behavior of the laminates, Cowell said. They were just published in Physica Status Solidi A, in work supported by the National Science Foundation.

“We haven’t yet used this approach to achieve negative refraction, but the findings suggest it should work for that,” he said. “That will be one goal of continuing research. No one had thought of using amorphous metals for this purpose. They didn’t think it could be that simple.”

Negative refraction, Cowell said, is a brilliant idea. It is based on the equations developed by the young physicist and mathematician Maxwell more than 150 years ago – work for which he is revered, along with Isaac Newton and Albert Einstein, as one of the greatest physicists who ever lived. Einstein kept a photograph of Maxwell on his office wall.

But for generations, theory is about all that it was. Just in the past decade have researchers finally figured out how to create materials of any type that can achieve negative refraction. A way to accomplish that at low cost for the commercial marketplace could be of considerable importance, scientists say.

One application of particular interest is a “super lens,” a device that might provide light magnification at levels that dwarf any existing technology. Many applications are possible in electronics manufacturing, lithography, biomedicine, insulating coatings, heat transfer, space applications, and perhaps new approaches to optical computing and energy harvesting.

The discovery of amorphous metamaterials is an outgrowth of recent findings at OSU about ways to create a metal-insulator-metal, or MIM diode, also of commercial significance. The OSU research is one of the latest advances in “dispersion engineering,” or the control of electromagnetic radiation.

About the OSU College of Engineering: The OSU College of Engineering is among the nation’s largest and most productive engineering programs. In the past six years, the College has more than doubled its research expenditures to $27.5 million by emphasizing highly collaborative research that solves global problems, spins out new companies, and produces opportunity for students through hands-on learning.

The "other" applications of metamaterials such as super lenses and energy harvesting have applications on the military side as well; high power optics that are much smaller and lighter than existing ones, and the ability to concentrate solar energy to make small man portable collectors that can generate useful amounts of energy when the sun is shining come to mind.
Dagny, this is not a battle over material goods. It's a moral crisis, the greatest the world has ever faced and the last. Our age is the climax of centuries of evil. We must put an end to it, once and for all, or perish - we, the men of the mind. It was our own guilt. We produced the wealth of the world - but we let our enemies write its moral code.