Scientists Claim to be "One Step Closer" to Invisibilty Cloak

Scientists yesterday announced that a team of researchers at the University of California, Berkeley is “one step closer” to developing an invisibility cloak capable of masking three-dimensional objects.

Prior to this past weekend, scientists had only managed to cloak very small, 2D objects, not exactly something you could use to smuggle your way across enemy lines.

What you see in front of you is all down to reflection of light. When you look at something, natural light bounces of the object and reflects a certain amount of light back to your eyes. Your eye focuses this image onto the retina — and bam — pictures.

Researchers claim to have come up with a way to redirect light around three-dimensional objects using metamaterials (mixtures of metal and circuit board materials such as ceramic, Teflon or fiber composite). Metamaterials are designed to bend light in a way that other materials don’t and scientist are attempting to use them to bend light around objects so they don’t cast a shadow or reflect light.

Using a simple example, negative refraction applied to a fish swimming in the water would make the fish appear to be "flying" above the water, rendering the fish in the water invisible. The problem is to find the "secret water" that manipulates the electromagnetic wavelength being used.

In the past, manipulation of wavelengths has been successful, however, only in the 2D space and in the longer microwave band of 1 mm to 30 cm, which compares to a wavelength of light visible to the human eye of 400 nm (violet and purple light) to 700 nm (deep red light). Infrared light wavelengths are longer, measuring from about 750 nm to 1 mm. (A human hair is about 100,000 nanometers in diameter.)

The metamaterial described is composed of silver nanowires grown inside porous aluminum oxide. Although the structure is about 10 times thinner than a piece of paper - a wayward sneeze could blow it away - it is considered a bulk metamaterial because it is more than 10 times the size of a wavelength of light. "The geometry of the vertical nanowires, which were equidistant and parallel to each other, were designed to only respond to the electrical field in light waves," said Jie Yao, a student in UC Berkeley’s Graduate Program in Applied Science and Technology and co-lead author of the study in Science. "The magnetic field, which oscillates at a perpendicular angle to the electrical field in a light wave, is essentially blind to the upright nanowires, a feature which significantly reduces energy loss."

Jason Valentine, UC Berkeley graduate student and co-lead author of the Nature paper, explained that each pair of conducting and non-conducting layers forms a circuit, or current loop. Stacking the alternating layers together creates a series of circuits that respond together in opposition to that of the magnetic field from the incoming light. "Natural materials do not respond to the magnetic field of light, but the metamaterial we created here does," Valentine said. "It is the first bulk material that can be described as having optical magnetism, so both the electrical and magnetic fields in a light wave move backward in the material."

The research, which is funded by the U.S. Army Research Office and the National Science Foundation’s Nano-Scale Science and Engineering Center is led by Xiang Zhang and will be published in Nature and Science later on this week.

(Via Associated Press)