Purdue researchers use AZO for optical metamaterials

Purdue researchers use AZO for optical metamaterials

MANHASSET, NY -- Researchers at Purdue University have shown how to create metamaterials without the traditional silver or gold previously required for creating optical metamaterials.

The Purdue researchers replaced the metals with an aluminum-doped zinc oxide (AZO). "This means we can have a completely new material platform for creating optical metamaterials, which offers important advantages," Alexandra Boltasseva, a Purdue University assistant professor of electrical and computer engineering. Boltasseva said, in a statement. "The doped oxide brings not only enhanced performance but also is compatible with semiconductors.”

The research team developed a new metamaterial consisting of 16 layers alternating between AZO and zinc oxide. Light passing from the zinc oxide to the AZO layers encounters an "extreme anisotropy," causing its dispersion to become "hyperbolic," which dramatically changes the light's behavior.

The researchers doped zinc oxide with aluminum which caused it to behave like a metal at certain wavelengths and like a dielectric at other wavelengths.

Using the silver and gold metals is impractical because of high cost and incompatibility with semiconductor manufacturing processes. The metals do not transmit light efficiently, causing much of it to be lost.
"The doped oxide brings not only enhanced performance but also is compatible with semiconductors," Boltasseva said.

The AZO also makes it possible to "tune" the optical properties of metamaterials, an advance that could hasten their commercialization.

"This could actually lead to a whole new family of devices that can be tuned or switched," Boltasseva said. "AZO can go from dielectric to metallic. So at one specific wavelength, at one applied voltage, it can be metal and at another voltage it can be dielectric. This would lead to tremendous changes in functionality."

"We anticipate that the development of these new plasmonic materials and nanostructured material composites will lead to tremendous progress in the technology of optical metamaterials," remarked Boltasseva.

The research paper was partly authored by Boltasseva, and others including Vladimir M. Shalaev, scientific director of nanophotonics at Purdue's Birck Nanotechnology Center, a distinguished professor of electrical and computer engineering and a scientific adviser for the Russian Quantum Center.

The research work has been funded in part by the U.S. Office of Naval Research, National Science Foundation and Air Force Office of Scientific Research.
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