These new findings could be important in transforming how light or other waves can be controlled or transmitted. Just as traditional wires gave way to fiber optics, the new meta-material could revolutionize the transmission of light and waves.
This is Nathan Landy with cloaking device.
Credit: Duke University Photography
Because the goal of this type of research involves taming light, a new field of transformational optics has emerged. The results of the Duke experiments were published online Nov. 11 in the journal Nature Materials.
The Duke team has extensive experience in creating "meta-materials," man-made objects that have properties often absent in natural ones. Structures incorporating meta-materials can be designed to guide electromagnetic waves around an object, only to have them emerge on the other side as if they had passed through an empty volume of space, thereby cloaking the object.
"In order to create the first cloaks, many approximations had to be made in order to fabricate the intricate meta-materials used in the device," said Nathan Landy, a graduate student working in the laboratory of senior investigator David R. Smith, William Bevan Professor of electrical and computer engineering at Duke's Pratt School of Engineering.
"One issue, which we were fully aware of, was loss of the waves due to reflections at the boundaries of the device," Landy said. He explained that it was much like reflections seen on clear glass. The viewer can see through the glass just fine, but at the same time the viewer is aware the glass is present due to light reflected from the surface of the glass. "Since the goal was to demonstrate the basic principles of cloaking, we didn't worry about these reflections."
Landy has now reduced the occurrence of reflections by using a different fabrication strategy. The original cloak consisted of parallel and intersecting strips of fiberglass etched with copper. Landy's cloak used a similar row-by-row design, but added copper strips to create a more complicated -- and better performing -- material. The strips of the device, which is about two-feet square, form a diamond-shape, with the center left empty.
When any type of wave, like light, strikes a surface, it can be either reflected or absorbed, or a combination of both. In the case of earlier cloaking experiments, a small percentage of the energy in the waves was absorbed, but not enough to affect the overall functioning of the cloak.
The cloak was naturally divided into four quadrants. Landy explained 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," Landy said. "After many calculations, we thought we could correct this situation by shifting each strip so that it met its mirror image at each interface.
"We built the cloak, and it worked," he said. "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."
Landy said this approach could have more applications than just cloaks. For example, meta-materials can "smooth out" twists and turns in fiber optics, in essence making them seem straighter. This is important, Landy said, because each bend attenuates the wave within it.
The researchers are now working to apply the principles learned in the latest experiments to three dimensions, a much greater challenge than in a two-dimensional device.
The Office of Naval Research and the Army Research Office supported the research.
CITATION: "A full-parameter unidirectional metamaterial cloak for microwaves," Nathan Landy and David R. Smith; Nature Materials, Nov. 12, 2012. DOI: 10.1038/nmat3476
Richard Merritt | EurekAlert!
Gelatine instead of forearm
19.04.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Computers create recipe for two new magnetic materials
18.04.2017 | Duke University
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...
Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.
A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
21.04.2017 | Physics and Astronomy
21.04.2017 | Health and Medicine
21.04.2017 | Physics and Astronomy