Tuesday, 03 Apr, 2007 Science

Using the nanotechnology scientists were able to make a significant step towards inventing an "optical cloaking", which represents a device able to make objects invisible. The device guides light around anything that is placed withing the so-called "cloak".

The engineers at Purdue University have followed mathematical guidelines that were devised last year by the UK physicists to create a theoretical design, which in its turn uses an array of very small needles. The latter radiate from a central spoke outwards.

The theoretical design looks like a round hairbrush. It would bend around any object that is "cloaked". Those objects that are situated in the background will be visible but the ones that are cloaked not. Vladimir Shalaev, the university's Robert and Anne Burnett Professor of Electrical and Computer Engineering, mentioned that the invisibility of the cloaked objects is provided by the cylindrical array of nano-needles.

Despite all the upper mentioned advantages, the theoretical design, however, according to Shalaev, has one significant limitation: it is can function only for a single wavelength. Thus it cannot work for the whole frequency range of the visible spectrum.

According to the calculations made by the researchers the device can make any object invisible if it is in a wavelength of 632.8 nanometers. This wavelength corresponds to the color red.

Shalaev says that it is quite possible to develop a design able to work for all colors of visible light. This, however, currently represents a big challenge for the scientists. "In principle, this cloak could be arbitrarily large, as large as a person or an aircraft", he said. This nanotechnological research is based at the Discovery Park of the Birck Nanotechnology Center at Purdue.

In 2006 several researchers published their findings on optical cloaking device. Shalaev mentioned that the mathematical requirements for the device were quite general, which is why together with his team he thought of fulfilling the requirements with a concrete and specific design.

Shalaev stated that his team is able to cloak objects regardless of their size. For this, however, scientists need two fulfill two requirements: one is that the light must not reflect off of the object and the second requirements is that the light must surround the whole object in a way so people would see only the background and not the object that is cloaked.

In case only the first requirement is fulfilled than you would to see a dark shape of the object, thus it would be clear that something was there. The most difficult task is to satisfy the second requirement, that is to bend the light around the cloaked object. When it is done you will see only the background. The whole device is made of, what scientists say, non-magnetic metamaterials.

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