Metamaterial Manipulates Light at Will

Much in the same way that electronics manipulate electrons, Duke University researchers have developed a material that allows them to manipulate light at will, a discovery that could help replace electronic components with optical technology.

Light-based devices would enable faster and more efficient transmission of information, similar to how optical fibers revolutionized the telecommunications industry by replacing wires.

Researchers Alec Rose and Da Huang of Duke University. (Images: Duke University Photography)

The breakthrough revolves around a metamaterial — a man-made structure that can be engineered to exhibit properties not readily found in nature. The structure used in these experiments resembles a miniature set of tan venetian blinds.

When light passes through a material, even though it may be reflected, refracted or weakened along the way, it is still the same light coming out — known as linearity.

"For highly intense light, however, certain 'nonlinear' materials violate this rule of thumb, converting the incoming energy into a brand new beam of light at twice the original frequency, called the second harmonic," said Alec Rose, a graduate student in the laboratory of David R. Smith, William Bevan professor of electrical and computer engineering at Duke's Pratt School of Engineering.

The metamaterial device.

As an example, he cited the crystal in some laser pointers, which transforms the normal laser light into another beam of a different color — the second harmonic. Although they contain nonlinear properties, designing such devices requires a great deal of time and effort to be able to control the direction of the second harmonic, and natural nonlinear materials are quite weak.

"Normally, this frequency-doubling process occurs over a distance of many wavelengths, and the direction in which the second harmonic travels is strictly determined by whatever nonlinear material is used," Rose said. "Using the novel metamaterials at microwave frequencies, we were able to fabricate a nonlinear device capable of 'steering' this second harmonic. The device simultaneously doubled and reflected incoming waves in the direction we wanted.

"This magnitude of control over light is unique to nonlinear metamaterials and can have important consequences in all-optical communications, where the ability to manipulate light is crucial," Rose said.

The research results were published online in the journal Physical Review Letters.

For more information, visit: www.duke.edu