The Journal of Young Investigators: An Undergraduate, Peer-Reviewed Science Journal
Volume 20, Issue 3. September 2010
Researchers Improve Upon Invisibility Cloak
![[i]Image Courtesy: Duke University[/i]](/articleimages/894/originals/img0.jpg)
Image Courtesy: Duke University
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26 January 2007 -
Addressing the limitations of the invisibility cloak announced last fall, researchers at the University of Rochester are now developing techniques to bring the device a step closer to becoming reality. The team, led by Allan Greenleaf, has shown that several key improvements can be made on the original design using theoretical mathematics.
In October 2006, David Smith and his colleagues at Duke University announced that they had created the world's first practical cloaking device. The team demonstrated that an object could be rendered invisible by the bending of electromagnetic radiation, which includes visible light as well as radio waves, microwaves, and X-rays. Once the realm only of science fiction and fantasy, an invisibility cloak, not unlike the one used by Harry Potter, was within sight.
Although the device built by David Smith at Duke was a tremendous achievement and was heralded in such publications as Science Magazine, Discover Magazine, and PC Magazine, it has several fundamental limitations. Greenleaf's work shows that these limitations can be overcome, at least in theory.
First, the cloak works only on passive objects, ones which do not emit electromagnetic radiation. The team at Duke used a copper cylinder (as the invisibility cloak?). For a true invisibility shield to be useful, however, it must also be able to cloak actively emitting objects—things like cell phones, computers, or even simpler devices like flashlights. The mathematics developed by Greenleaf allow for the cloaking of such objects.
Second, the invisibility shield works at only a very narrow range of wavelengths. "Given the current technology, when we talk about invisibility, we're talking only about being invisible at just a narrow range of wavelengths," says Greenleaf. "For example, an object could be rendered invisible at just a specific wavelength of red; it would be visible in nearly every other color." This also means that an object could be invisible to some radiation, like X-rays or radio waves, and not to visible light.
This was exactly the case at Duke. Smith's team shielded their copper cylinder only from a specific band of microwaves, meaning it was entirely visible to the naked eye. Greenleaf's advances allow for shielding at all frequencies, an essential requirement for any real-world invisibility cloak.
Greenleaf suggests that using two layers of material for the cloaking device would solve both of these difficulties. "In this case, we basically put the metamaterials on the outside of the device, and we make a similar 'matched' construction inside the device and point it inwards."
On December 6, 2006 Greenleaf and Smith met to discuss translating Greenleaf's theories into reality. "Allan has been looking at the problem much more generally, and deriving the conditions for when true invisibility is or is not possible," says Smith. "We are very interested in what he and his colleagues come up with!"
Cloaking actively emitting objects at all wavelengths of light will ultimately lead to a true invisibility shield. Such a device would have widespread applications in defense, communications, and other industries.
For more information about the Duke team, see the article "Now You See Me, Now You Don't" by Kirsten Schuck.
- Kevin Rio
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Comments:
This article is well written. I especially liked the analogy to Harry Potter - someone that immediately comes to mind with words "invisibility cloak". I wonder how difficult it will be to make something invisible at all wavelengths though.
The article was well written but the same stuff that it cannot be seen in a
particular spectrum was repeated that is what I felt .It was a very
innovative article .
Great job updating and bringing us up to speed on this important find. I think you portray the limitations of the device realistically and show how researchers are collaborating to overcome those limitations. some improvements: the funny little parentheses after mentioning the copper plate as the cloak seems a little out of place. I don't think it matches the tone of the article, which is kind of serious. This is a fun discovery so maybe a more lighthearted tone would suit this better. But the facts were covered very well and important features placed in the beginning.
In October 2006, David Smith and his colleagues at Duke University announced that they had created the world's first practical cloaking device. The team demonstrated that an object could be rendered invisible by the bending of electromagnetic radiation, which includes visible light as well as radio waves, microwaves, and X-rays. Once the realm only of science fiction and fantasy, an invisibility cloak, not unlike the one used by Harry Potter, was within sight.
Although the device built by David Smith at Duke was a tremendous achievement and was heralded in such publications as Science Magazine, Discover Magazine, and PC Magazine, it has several fundamental limitations. Greenleaf's work shows that these limitations can be overcome, at least in theory.
First, the cloak works only on passive objects, ones which do not emit electromagnetic radiation. The team at Duke used a copper cylinder (as the invisibility cloak?). For a true invisibility shield to be useful, however, it must also be able to cloak actively emitting objects—things like cell phones, computers, or even simpler devices like flashlights. The mathematics developed by Greenleaf allow for the cloaking of such objects.
Second, the invisibility shield works at only a very narrow range of wavelengths. "Given the current technology, when we talk about invisibility, we're talking only about being invisible at just a narrow range of wavelengths," says Greenleaf. "For example, an object could be rendered invisible at just a specific wavelength of red; it would be visible in nearly every other color." This also means that an object could be invisible to some radiation, like X-rays or radio waves, and not to visible light.
This was exactly the case at Duke. Smith's team shielded their copper cylinder only from a specific band of microwaves, meaning it was entirely visible to the naked eye. Greenleaf's advances allow for shielding at all frequencies, an essential requirement for any real-world invisibility cloak.
Greenleaf suggests that using two layers of material for the cloaking device would solve both of these difficulties. "In this case, we basically put the metamaterials on the outside of the device, and we make a similar 'matched' construction inside the device and point it inwards."
On December 6, 2006 Greenleaf and Smith met to discuss translating Greenleaf's theories into reality. "Allan has been looking at the problem much more generally, and deriving the conditions for when true invisibility is or is not possible," says Smith. "We are very interested in what he and his colleagues come up with!"
Cloaking actively emitting objects at all wavelengths of light will ultimately lead to a true invisibility shield. Such a device would have widespread applications in defense, communications, and other industries.
For more information about the Duke team, see the article "Now You See Me, Now You Don't" by Kirsten Schuck.
- Kevin Rio
-------------------------------------------------------
Comments:
This article is well written. I especially liked the analogy to Harry Potter - someone that immediately comes to mind with words "invisibility cloak". I wonder how difficult it will be to make something invisible at all wavelengths though.
The article was well written but the same stuff that it cannot be seen in a
particular spectrum was repeated that is what I felt .It was a very
innovative article .
Great job updating and bringing us up to speed on this important find. I think you portray the limitations of the device realistically and show how researchers are collaborating to overcome those limitations. some improvements: the funny little parentheses after mentioning the copper plate as the cloak seems a little out of place. I don't think it matches the tone of the article, which is kind of serious. This is a fun discovery so maybe a more lighthearted tone would suit this better. But the facts were covered very well and important features placed in the beginning.
Journal of Young
Investigators. 2008. Volume 0.
Copyright © 2008 by Rio Kevin and and JYI. All rights reserved.
Copyright © 2008 by Rio Kevin and and JYI. All rights reserved.