New Metamaterial Creates Practical, Tunable Devices

A novel metamaterial can easily be integrated into semiconductor electronics, which could advance sensors, solar collectors, quantum computing and optical cloaks, and could lead to devices that make optical microscopes 10 times more powerful.

Noble metals such as silver and gold are commonly used in the production of metamaterials, but these metals are very expensive and cannot be integrated into current semiconductor electronics technologies.

Researchers led by Alexandra Boltasseva at Purdue University replaced the noble metals with aluminum-doped zinc oxide, or AZO. The metamaterial consists of 16 alternating layers of AZO and regular zinc oxide. Light that passes from one layer to another encounters extreme anisotropy, causing its dispersion to be hyperbolic and its behavior to be extremely altered.

Doping the zinc oxide alters its optical properties and causes it to behave as a metal at certain wavelengths of light, and as a dielectric at other wavelengths. This makes it possible to tune the optical properties of materials, making them versatile and easy to commercialize.

"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."

Current technologies are limited, because without metamaterials, electronic components cannot be smaller than the wavelengths of light. Using AZO also allows components to work in the near-infrared range, which is usable for optical communications, and can create a new generation of devices for harvesting light for solar energy applications.

"Alternative plasmonic materials such as AZO overcome the bottleneck created by conventional metals in the design of optical metamaterials and enable more efficient devices," she said. "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, enabling the full-scale development of this technology and uncovering many new physical phenomena."

The findings were published in the May 14 issue of the Proceedings of the National Academy of Sciences in a paper co-authored by doctoral students Gururaj V. Naik and Jingjing Liu, senior research scientist Alexander V. Kildishev and Vladimir M. Shalaev, scientific director of nanophotonics at Purdue's Birck Nanotechnology Center.

The research was funded in part by the Office of Naval Research, the National Science Foundation and the Air Force Office of Scientific Research.

For more information, visit: www.purdue.edu