Researchers at Oregon State University have discovered a way to make a low-cost material that might accomplish negative refraction of light and other radiation – a goal first theorized in 1861 by a giant of science, Scottish physicist James Maxwell, that has still eluded wide practical use.
Other materials can do this but they are based on costly, complex crystalline materials. A low-cost way that yields the same result will have extraordinary possibilities, experts say – ranging from a “super lens” to energy harvesting, machine vision or “stealth” coatings for seeming invisibility.
The new approach uses ultra-thin, ultra-smooth, all-amorphous laminates, essentially a layered glass that has no crystal structure. It is, the researchers say, a “very high-tech sandwich.” The goal is to make radiation bend opposite to the way it does when passing through any naturally occurring material.
Dispersion engineering – New nano-scale amorphous laminates discovered at Oregon State University are the latest advance in the control of light through solid materials, or dispersion engineering. The work is an important step toward a “super lens.” (Graphic courtesy of Oregon State University)
“To accomplish the task of negative refraction, these metamaterials have to be absolutely perfect, just flawless,” said Bill Cowell, a doctoral candidate in the OSU School of Electrical Engineering and Computer Science. “Everyone thought the only way to do that was with perfectly crystalline materials, which are quite expensive to produce and aren’t very practical for large-area commercial application.
“We now know these materials may not need to be that exotic.”
The new study has explained how easy-to-produce laminate materials, created with technology similar to that used to produce a flat panel television, should work for this purpose. The findings outline the component materials and the theoretical behavior of the laminates, Cowell said.
“We haven’t yet used this approach to achieve negative refraction, but the findings suggest it should work for that,” he said. “That will be one goal of continuing research. No one had thought of using amorphous metals for this purpose. They didn’t think it could be that simple.”
One application of particular interest is a “super lens,” a device that might provide light magnification at levels that dwarf any existing technology. Many applications are possible in electronics manufacturing, lithography, biomedicine, insulating coatings, heat transfer, space applications, and perhaps new approaches to optical computing and energy harvesting.
Nanolaminates built from ultra-thin, ultra-smooth films of amorphous metals, and solution-processed oxides represent a new platform for dispersion engineering. Materials exhibiting anisotropic elliptical dispersion and hyperbolic dispersion with positive refraction are realized through choice of amorphous metal and laminate design. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), polarized reflectance measurements, and effective medium theory are combined to demonstrate the precision and predictability of the fabrication techniques and optical properties from ultra-violet to infra-red frequencies.
Engineering anisotropic dielectric response through amorphous laminate structures.