Improved invisibility cloak developed

Six years after electrical engineers from Duke University created a functional albeit still imperfect invisibility cloak, a member of the team has improved on the device's design.

 

A report on ScienceDaily.com said the development - done by adding copper strips to the cloaking material - could lead to a new field of "transformational optics."

 

The results of the Duke experiments were published online Nov. 11 in the journal Nature Materials.

 

"We built the cloak, and it worked. It split light into two waves which traveled around an object in the center and re-emerged as the single wave with minimal loss due to reflections," said Nathan Landy, a graduate student working in the laboratory of senior investigator David Smith, William Bevan Professor of electrical and computer engineering at Duke's Pratt School of Engineering.

 

He said that in making the first cloaks, many approximations had to be made to fabricate the intricate meta-materials used in the device.

 

"One issue, which we were fully aware of, was loss of the waves due to reflections at the boundaries of the device," eh said.

 

Meta-materials

 

Initially, the Duke team created "meta-materials," artificial materials with properties often absent in natural ones, which can guide electromagnetic waves around an object.

 

The electromagnetic waves are to emerge on the other side as if they had passed through an empty volume of space, thereby cloaking the object, ScienceDaily.com said.

 

Landy compared the phenomenon to reflections seen on clear glass, where the viewer can see through the glass but is aware the glass is present because of light reflected from the surface of the glass.

Modifications  

He has reduced the occurrence of reflections by using a different fabrication strategy - adding copper strips to the original cloak, which consisted of parallel and intersecting strips of fiberglass etched with copper.

 

This would create a better-performing material, with the strips measuring two feet square, forming a diamond shape, with the center left empty.

 

With the new device, when light strikes a surface, it can be reflected or absorbed, or both. Earlier cloaking experiments had shown a small percentage of the energy in the waves was absorbed, but not enough to affect the functioning of the cloak.

 

Reflections

 

Landy added the "reflections" noted in earlier cloaks tended to occur along the edges and corners of the spaces within and around the meta-material.

 

"Each quadrant of the cloak tended to have voids, or blind spots, at their intersections and corners with each other. After many calculations, we thought we could correct this situation by shifting each strip so that it met its mirror image at each interface," he said.

 

Applications

 

Landy said this approach could have more applications than just cloaks.

 

He suggested meta-materials can "smooth out" twists and turns in fiber optics, making them seem straighter.

 

ScienceDaily.com said the researchers are now working to apply the principles to three dimensions. — TJD, GMA News