novel negative-index metamaterial that responds to visible light designed

[n2doc]

Caltech-led team designs novel negative-index metamaterial that responds to visible light

Published: Thursday, April 22, 2010 - 16:30 in Physics & Chemistry

A group of scientists led by researchers from the California Institute of Technology (Caltech) has engineered a type of artificial optical material—a metamaterial—with a particular three-dimensional structure such that light exhibits a negative index of refraction upon entering the material. In other words, this material bends light in the "wrong" direction from what normally would be expected, irrespective of the angle of the approaching light. This new type of negative-index metamaterial (NIM), described in an advance online publication in the journal Nature Materials, is simpler than previous NIMs—requiring only a single functional layer—and yet more versatile, in that it can handle light with any polarization over a broad range of incident angles. And it can do all of this in the blue part of the visible spectrum, making it "the first negative index metamaterial to operate at visible frequencies," says graduate student Stanley Burgos, a researcher at the Light-Material Interactions in Energy Conversion Energy Frontier Research Center at Caltech and the paper's first author.

"By engineering a metamaterial with such properties, we are opening the door to such unusual—but potentially useful—phenomena as superlensing (high-resolution imaging past the diffraction limit), invisibility cloaking, and the synthesis of materials index-matched to air, for potential enhancement of light collection in solar cells," says Harry Atwater, Howard Hughes Professor and professor of applied physics and materials science, director of Caltech's Resnick Institute, founding member of the Kavli Nanoscience Institute, and leader of the research team

What makes this NIM unique, says Burgos, is its engineering. "The source of the negative-index response is fundamentally different from that of previous NIM designs," he explains. Those previous efforts used multiple layers of "resonant elements" to refract the light in this unusual way, while this version is composed of a single layer of silver permeated with "coupled plasmonic waveguide elements."

Surface plasmons are light waves coupled to waves of electrons at the interface between a metal and a dielectric (a non-conducting material like air). Plasmonic waveguide elements route these coupled waves through the material. Not only is this material more feasible to fabricate than those previously used, Burgos says, it also allows for simple "tuning" of the negative-index response; by changing the materials used, or the geometry of the waveguide, the NIM can be tuned to respond to a different wavelength of light coming from nearly any angle with any polarization. "By carefully engineering the coupling between such waveguide elements, it was possible to develop a material with a nearly isotopic refractive index tuned to operate at visible frequencies."

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http://esciencenews.com/articles/2010/04/22/caltech.led.team.designs.novel.negative.index.metamaterial.responds.visible.light

[Duer 157099]

1. Reading things like that is such a refreshing change from

most other topics on DU. It reminds me that just maybe, there is hope for humanity.

Science rocks. :thumbsup:

[Ready4Change]

2. So, this only works in a narrow wavelength band?

Seems to say they've engineered it for blue in the visible spectrum. Is that useful?

(I mean, unless you happen to be a member of the Blue Man group who want's to sneak in some place? :P )

[n2doc]

3. It's a step in the process

First it only worked for really short wavelength radiation (microwaves), but they have gotten this to work for visible light. Eventually they will get it to work for all wavelengths and off we go...