A magic cloak

This PhysicsWeb article describes a very fun proposal for invisibility cloaks. Come to think of it, the principle is simple: cover your object with a material than bends light coming from its rear around the body and forwards it afterwards reversing the deviation.
Snell-1Not surprisingly, the idea was “inspired by the geometry of curved space — a discipline that is normally in the firm hands of researchers in general relativity.” The tricky part is, of course, finding a material with the right behaviour. The feat seems to be possible thanks to the so-called metamaterials, which may have negative-index refraction. As shown in the figure on the right (taken from the link above), according to Snell’s law, a material with a negative index of refraction is able to reflect light through negative angles with respect to the surface’s normal. As you can see, with an apt enough arrangement of such prisms, you can obtain the needed light twist around the cloaked object. Curious? More on negative index refraction in this list of publications.


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