Metamaterials Hold Promise For Invisibility Cloaks
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The Berkeley researchers stacked layers of silver and nonconducting magnesium fluoride and cut nanoscale-sized fishnet patterns into them for the metamaterials. They measured a negative index of refraction at wavelengths as short as 1,500 nanometers, or the near-infrared light range, according to a university announcement.
The researchers also demonstrated a second method of negatively refracting light. They used silver nanowires grown inside porous aluminum oxide to create a structure about one-tenth the thickness of a sheet of paper. The metamaterial refracted red light wavelengths as short as 660 nanometers, according to the researchers.
"The geometry of the vertical nanowires, which were equidistant and parallel to each other, were designed to only respond to the electrical field in light waves," Jie Yao, a student in UC Berkeley's Graduate Program in Applied Science and Technology and co-lead author of the study in Science, explained. "The magnetic field, which oscillates at a perpendicular angle to the electrical field in a light wave, is essentially blind to the upright nanowires, a feature which significantly reduces energy loss."
"What makes both these materials stand out is that they are able to function in a broad spectrum of optical wavelengths with lower energy loss," Zhang said. "We've also opened up a new approach to developing metamaterials by moving away from previous designs that were based upon the physics of resonance. Previous metamaterials in the optical range would need to vibrate at certain frequencies to achieve negative refraction, leading to strong energy absorption. Resonance is not a factor in both the nanowire and fishnet metamaterials."
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UCal-Berkeley is approaching the metamaterial issue by using silver and magnesium flouride. This is very novel in that previous research has focused on the plasmonic capability of gold.
Something else that seems interesting to me is the school that this is being done at: UCal - Berkeley. The home of Dr. Robert Baker, one of my favorite names to Google.