Metascreen Makes Invisibility Cloaks A Potential Reality
March 26, 2013

Invisibility Cloak Method Brings Harry Potter’s Cloak Into Reality

Lee Rannals for — Your Universe Online

Harry Potter had one, and maybe one day so will you, if the new invisibility cloak method described in the New Journal of Physics comes to fruition.

US researchers have developed a new cloak that is just micrometers thick and is able to hide three-dimensional objects from microwaves in their natural environment, in all directions from all the observers' positions.

Previously, scientists have developed invisibility cloaks that have been fairly bulky concepts. However, this new concept is much thinner, making Harry Potter's cloak read about in the book series and seen on screen a more attainable reality.

The University of Texas at Austin team used a new, ultra-thin layer known as "metascreen" to help hide people. The cloak is made by attaching strips of 66 µm-thick copper tape to a 100 µm-thick polycarbonate film in a fishnet design. The team used it to cloak a 7-inch cylindrical rod from microwaves and showed optimal functionality when the microwaves were at a frequency of 3.6 GHz and over a moderately broad bandwidth.

The team predicts due to the inherent conformability of the metascreen and the robustness of the proposed technique, oddly shaped and asymmetrical objects are able to be cloaked with the same principles.

We are able to detect objects because of the light rays bouncing off their surface towards our eyes as our eyes process this information. Previous cloaking studies used metamaterials to divert the incoming waves around an object. The new method uses an ultra-thin, metallic metascreen to cancel out the waves as they are scattered off the cloaked object.

"When the scattered fields from the cloak and the object interfere, they cancel each other out and the overall effect is transparency and invisibility at all angles of observation," said co-author of the study Professor Andrea Alu.

"The advantages of the mantle cloaking over existing techniques are its conformability, ease of manufacturing and improved bandwidth. We have shown that you don't need a bulk metamaterial to cancel the scattering from an object — a simple patterned surface that is conformal to the object may be sufficient and, in many regards, even better than a bulk metamaterial."

He said this technique could be used to cloak light, and added this concept could put us closer to a practical realization one day.

"However, the size of the objects that can be efficiently cloaked with this method scales with the wavelength of operation, so when applied to optical frequencies we may be able to efficiently stop the scattering of micrometer-sized objects," Alu said. "Still, we have envisioned other exciting applications using the mantle cloak and visible light, such as realizing optical nanotags and nanoswitches, and noninvasive sensing devices, which may provide several benefits for biomedical and optical instrumentation."

In order for an object to vanish from eyesight, a cloak would have to simultaneously interact with all of the wavelengths that make up light. An invisibility cloak would need to divert light within it so the light avoids a certain volume or void within an object that could be placed in the cloak. A study published in 2011 opened up the possibility for a potential invisibility cloak wearer to move around among an ever-changing background.

Janos Perczel's concept opened up further possibilities for the design of a practical invisibility cloak that overcomes the problem of light speed that other advances have struggled to address.