Transform a ball into a rock -- or make it invisible -- using transformation optics

Jul 09, 2009 By Miranda Marquit feature
Image from Phys. Rev. Lett. 102, 253902 (2009). (c)2009 APS. Reprinted with permission.

( -- Science fiction and fantasy tales are full of the ability to "cloak" characters with invisibility. Whether it is a spaceship with a cloaking device, or a young wizard with an invisibility cloak, the interest in rendering someone or something invisible captures our fancy. Scientists have succeeded in creating the illusion of invisibility by bending light around a region for concealment. These types of devices have limitations, however; one of these limitation that the device normally has to be touching the object to be rendered invisible - or in very close proximity.

Instead of bending light, though, what if transformation optics was used to create invisibility - or even give an object the appearance of a completely different object? A team of theorists at the Hong Kong University of Science and Technology propose a technique that might be able to accomplish just that, with a remote device. The group’s proposal appears in : “ Optics: The Optical Transformation of an Object into Another Object.”

“Right now, invisibility devices bend light, steering it around an object to make it appear transparent, as if it weren’t there,” Che Ting Chan tells Chan is one of the scientists who proposed the idea of a device that would use illusion optics to transform objects within a confined space. “Our proposed device would have special properties. It would employ a type of illusion that makes an object look exactly like another object.”

, which are manmade with special properties, would be used. A “complementary medium” would be employed to optically cancel a specified area. Then, a “restoring medium” would be used to make the cancelled space “reappear” as something else. For invisibility, the restored area would look like air. “If it looks like air,” Chan explains, “then it is transparent. You can see through it. It is like making something .” This method could also, theoretically, be used to “transform” objects. “You could make a ball look like a rock,” Chan says. “You could hide something in plain sight, as something else.”

In addition to transforming the way an object looks to others, this device would have another advantage over current invisibility devices. “You wouldn’t have to need the device to touch the object being hidden,” Chan insists. “You could remotely control a particular area to entirely exclude a specific wave without having to be as close.”

While the device sounds promising, Chan admits that there are difficulties involved in building such a cloak. “In addition to positive refractive material, which is not a big problem, we would require a negative refractive index.” Positive refractive materials are easily made, but something with a negative refractive index would require special design. “Some sort of structure to create a phase delay would be needed,” Chan says.

Chan and the Hong Kong team are working on interesting experimentalists in the concept. “We are dealing with electromagnetic waves,” Chan explains, “but there are those who are doing similar experiments with acoustic waves. Maybe if our idea was applied to acoustic waves first, it would be easier to see how to extend it to include light.”

More Information: Yun Lai, Jack Ng, HuanYang Chen, DeZhuan Han, JunJun Xiao, Zhao-Qing Zhang, and C.T. Chan, “Illusion Optics: The Optical Transformation of an Object into Another Object,” Physical Review Letters (2009). Available online: .

Copyright 2009
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of

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5 / 5 (5) Jul 10, 2009
This is another case of some scientists describing a mechanism for doing something with absolutely no idea how they would do it in reality. Yeh man, we'd like, cancel out the light waves, we could like turn a man into a woman. Yeh man, pass the munchies.
2 / 5 (1) Jul 10, 2009
Sorry, TBY.

Like they say, it just needs 'meta-materials', which is stuff patterned 'tighter' than the wavelengths involved.

Per Clarke's Law, 'sufficiently advanced technology is indistinguishable from magic'. Go Google...
5 / 5 (3) Jul 10, 2009
I have a letter from ACC himself when he replied to something I'd written to him in the early 1980s. May even be worth something now.

My point was that "just needs meta-materials" is a bit like saying "in order to fly you 'just' need to be able to suppress gravity" - the clever bit is not describing what you need to do, it's doing it.

There are lots of quaotation marks around the words in the article, which leads me to think it's more speculative than any new discovery.
1 / 5 (1) Jul 10, 2009
Oh, I get it! This isn't science, it is "magic" and therefore is justifiable reportage.

"speculative" is being generous.

Try - "a load of foolish babble".

not rated yet Jul 15, 2009
If to create a full invisibility of the subject by using metamaterials, one can still notice its presence
when the subject starts to move. Its movement will create different index of refraction for
observer in relation to the subjects that can be seen through the invisible moving subject.
For this reasons those subjects will start to blink. I noticed that effect by observing AFOs (Aliens Flying Object) that using the same technique,
in the night sky at altitude 20 - 40 miles. AFOs are invisible but when they move under the star the latter start to blink and their invisible bodies
surrounded by weak signal lights creating a circle. That is how I know that the reason for the existence of blinking stars is not only
different layers of atmosphere but also the presence of the moving AFOs.
not rated yet Jul 19, 2009
I propose a new technology that will enable me to pull money out of my posterior. There is one stumbling block I have to overcome first, it is completely impossible.
1 / 5 (1) Jul 21, 2009
This article is not worthy of appearing on PhysOrg. It should (at most) be in a childrens' book, or a gossip weekly.

Either Chan had something, and the PhysOrg editor missed it, or Chan is just waving his hands in the air.

Whatever the case, this article is a waste of PhysOrg's readers' time.

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