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Other research teams have previously developed metamaterials that function at optical frequencies, but those 2-D materials have been limited to a single monolayer of artificial atoms whose light-bending properties cannot be defined. Or, to give another example, a fish swimming underwater would instead appear to be moving in the air above the water's surface. If water exhibited negative refraction, the submerged portion of the pole would instead appear to jut out from the water's surface. In a classic illustration of how refraction works, the submerged part of a pole inserted into water will appear as if it is bent up towards the water's surface. In contrast, all materials found in nature have a positive refractive index, a measure of how much electromagnetic waves are bent when moving from one medium to another. The common thread in such metamaterials is negative refraction. For optical microscopes to discern individual, living viruses or DNA molecules, the resolution of the microscope must be smaller than the wavelength of light. In the case of invisibility cloaks or shields, the material would need to curve light waves completely around the object like a river flowing around a rock. (Jason Valentine/UC Berkeley)Īpplications for a metamaterial entail altering how light normally behaves. The alternating layers form small circuits that can bend light backwards. Below is a scanning electron microscope image of the fabricated structure, developed by UC Berkeley researchers. 15 issue of Science.Ībove is a schematic of the first 3-D "fishnet" metamaterial that can achieve a negative index of refraction at optical frequencies. 13 advanced online issue of Nature, and in the Aug. Two breakthroughs in the development of metamaterials - composite materials with extraordinary capabilities to bend electromagnetic waves - are reported separately this week in the Aug. Invisibility shields one step closer with new metamaterials that bend light backwardsīy Sarah Yang, Media Relations | 11 August 2008īERKELEY – Scientists at the University of California, Berkeley, have for the first time engineered 3-D materials that can reverse the natural direction of visible and near-infrared light, a development that could help form the basis for higher resolution optical imaging, nanocircuits for high-powered computers, and, to the delight of science-fiction and fantasy buffs, cloaking devices that could render objects invisible to the human eye. An illustration of how a fish in water is seen by an observer, with the red lines marking the refraction of light and the purple lines representing the path towards the perceived location of the fish, which appears above its actual location.