In the Science paper, the metamaterial takes another approach to bending light backwards. It is composed of silver nanowires grown inside porous aluminum oxide, the scientists said. They acknowledged that the structure is about 10 times thinner than a piece of paper, but it is still considered a bulk metamaterial because it is more than 10 times the size of a wavelength of light.
The authors of the paper said that they observed negative refraction from red light wavelengths as short as 660 nanometers, marking the first demonstration of bulk media bending visible light backwards. The innovation of this nanowire material, researchers said, is that it finds a new way to bend light backwards without technically achieving a negative index of refraction.
Both the nanowire and fishnet metamaterials can potentially play a key role, the researchers said, for most of the applications touted for metamaterials, such as nanoscale optical imaging or cloaking devices, said the researchers.
Here is a schematic and two scanning electron microscope images with top and side views of a metamaterial developed by UC Berkeley researchers. The material is composed of parallel nanowires embedded inside porous aluminum oxide. As visible light passes through the material, it is bent backwards in a phenomenon known as negative refraction.
