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News Picks : Invisibility cloak that works in fog

By: Physics Today
06 June 2014
Science: Although a variety of cloaking devices have been created since the idea was first proposed by theorists in 2006, each has its limitations. Some work only when using a single light wavelength, when the light is polarized in just one direction, or when viewed from a certain angle. Now researchers at Karlsruhe Institute of Technology in Germany have developed a cloak that is both broadband and omnidirectional and can hide a macroscopic object. However, it works only in diffusive, light-scattering media, such as fog. The cloak consists of a metal tube painted white on the outside and coated on the inside with an organic polymer doped with light-scattering microparticles. When placed in a tank of water saturated with white paint and backlit with white light, the cloak “hides” objects in its hollow core by allowing the light to diffuse through it faster than it can diffuse through the surrounding medium. Because the foggy conditions already obscure the object to a certain extent, such a cloaking device would have only limited applications, such as in the backlighting of displays.


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