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Blacker-Than-Black Corrugated Metamaterials
Researchers have discovered that a hyperbolic metamaterial with a corrugated surface has very low reflectance: ordinary black paint absorbs about 85% of incident light, whereas the new material absorbs up to 99% of incident light. It's blacker than black!
In their study, the researchers fabricated a hyperbolic metamaterial out of arrays of silver nanowires grown in alumina membranes. They found that this material absorbed about 80% of incoming light. Then, they ground the surface of the metamaterial to produce corrugations and defects, which they predicted would dramatically reduce the light reflection, increasing the absorption. Their measurements showed that the corrugated metamaterial absorbed up to 99% of incoming light, and that the radiation-absorbing capability is applicable to all parts of the electromagnetic spectrum.
(Hyperbolic metamaterial with a corrugated surface [pdf])
Panel (a): the phase space “volume” enclosed by two different surfaces of constant frequency, in the cases when components of the dielectric permittivity tensor are all positive (left) and have opposite signs (right).
Panel (b): angular reflectance profiles measured on untreated (circles) and roughened (diamonds) parts of the same membrane sample in spolarization and p-polarization. Inset: reflectance profiles in the corrugated sample (same as in main panel (b), zoomed).
Panels (c) and (d): topography profiles of the untreated (c) and corrugated (d) samples.
These metamaterials will make possible a variety of applications ranging from radar stealth technology to high-efficiency solar cells and photodetectors.
Science fiction fans have been shown a variety of "blacker-than-black" materials. For example, TMA-1, the Tycho monolith from Arthur C. Clarke's 1968 novel 2001: A Space Odyssey is described as follows:
The object before which the spacesuited man was posing was a vertical slab of jet-black material, about ten feet high and five feet wide: it reminded Floyd, somewhat ominously, of a giant tombstone. Perfectly sharp-edged and symmetrical, it was so black it seemed to have swallowed up the light falling upon it; there was no surface detail at all.
More recent authors have been more specific. The absolute black from Restaurant at the End of the Universe (Douglas Adams, 1980) and fuligin from Gene Wolfe's 1980 classic The Shadow of the Torturer are good examples.
Update 10-Nov-2011: Here's an early reference to the idea of a "blacker than black" coating for materials; see the black coating from E.E. 'Doc Smith's 1939 novel Gray Lensman. Thanks to Winchell Chung of Project Rho for the tip on this item. End update.
From Physics arXiv via Physorg.
Scroll down for more stories in the same category. (Story submitted 10/1/2011)
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