Metamaterials found to work for visible light

January 4, 2007

Ames Laboratory researchers have found the first metamaterial known to work for visible light, announcing the discovery in the Jan. 5 issue of Science.

For the first time ever, researchers at the U.S. Department of Energy's Ames Laboratory have developed a material with a negative refractive index for visible light. Ames Laboratory senior physicist Costas Soukoulis, working with colleagues in Karlsruhe, Germany, designed a silver-based, mesh-like material that marks the latest advance in the rapidly evolving field of metamaterials, materials that could lead to a wide range of new applications as varied as ultrahigh-resolution imaging systems and cloaking devices.

The discovery, detailed in the Jan. 5 issue of Science and the Jan. 1 issue of Optic Letters, and noted in the journal Nature, marks a significant step forward from existing metamaterials that operate in the microwave or far infrared – but still invisible –regions of the spectrum. Those materials, announced this past summer, were heralded as the first step in creating an invisibility cloak.

Metamaterials, also known as left-handed materials, are exotic, artificially created materials that provide optical properties not found in natural materials. Natural materials refract light, or electromagnetic radiation, to the right of the incident beam at different angles and speeds. However, metamaterials make it possible to refract light to the left, or at a negative angle. This backward-bending characteristic provides scientists the ability to control light similar to the way they use semiconductors to control electricity, which opens a wide range of potential applications.

"Left-handed materials may one day lead to the development of a type of flat superlens that operates in the visible spectrum," said Soukoulis, who is also an Iowa State University Distinguished Professor of Liberal Arts and Sciences. "Such a lens would offer superior resolution over conventional technology, capturing details much smaller than one wavelength of light to vastly improve imaging for materials or biomedical applications," such as giving researchers the power to see inside a human cell or diagnose disease in a baby still in the womb.

The challenge that Soukoulis and other scientists who work with metamaterials face is to fabricate them so that they refract light at ever smaller wavelengths. The "fishnet" design developed by Soukoulis' group and produced by researchers Stefan Linden and Martin Wegener at the University of Karlsruhe was made by etching an array of holes into layers of silver and magnesium fluoride on a glass substrate. The holes are roughly 100 nanometers wide. For some perspective, a human hair is about 100,000 nanometers in diameter.

"We have fabricated for the first time a negative-index metamaterial with a refractive index of -0.6 at the red end of the visible spectrum (wavelength 780 nm)," said Soukoulis. "This is the smallest wavelength obtained so far."

While the silver used in the fishnet material offers less resistance when subjected to electromagnetic radiation than the gold used in earlier materials, energy loss is still a major limiting factor. The difficulties in manufacturing materials at such a small scale also limit the attempts to harness light at ever smaller wavelengths.

"Right now, the materials we can build at THz and optical wavelengths operate in only one direction," Soukoulis said, "but we've still come a long ways in the six years since negative-index materials were first demonstrated."

"However, for applications to come within reach, several goals need to be achieved," he added. "First, reduction of losses by using crystalline metals and/or by introducing optically amplifying materials; developing three-dimensional isotropic designs rather than planar structures; and finding ways of mass producing large-area structures."

Source: Ames Laboratory

Explore further: New mirror reflects light differently than conventional mirrors

Related Stories

Beyond good vibrations: New insights into metamaterial magic

November 6, 2017

If invisibility cloaks and other gee-whiz apps are ever to move from science fiction to science fact, we'll need to know more about how these weird metamaterials actually work. Michigan Tech researcher Elena Semouchkina has ...

Synthetic material acts like an insect cloaking device

November 3, 2017

Synthetic microspheres with nanoscale holes can absorb light from all directions across a wide range of frequencies, making them a candidate for antireflective coatings, according to a team of Penn State engineers. The synthetic ...

Gold nano-arrows form basis of exotic new superstructures

October 30, 2017

(Phys.org)—A team of researchers at Peking University has found that tiny arrows made of gold can be used to create exotic new superstructures. In their paper published on the open access site Science Advances, the team ...

Recommended for you

How the Earth stops high-energy neutrinos in their tracks

November 22, 2017

Neutrinos are abundant subatomic particles that are famous for passing through anything and everything, only very rarely interacting with matter. About 100 trillion neutrinos pass through your body every second. Now, scientists ...

Quantum internet goes hybrid

November 22, 2017

In a recent study published in Nature, ICFO researchers led by ICREA Prof. Hugues de Riedmatten report an elementary "hybrid" quantum network link and demonstrate photonic quantum communication between two distinct quantum ...

Enhancing the quantum sensing capabilities of diamond

November 22, 2017

Researchers have discovered that dense ensembles of quantum spins can be created in diamond with high resolution using an electron microscopes, paving the way for enhanced sensors and resources for quantum technologies.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.