From graphene to invisibility (not in the visible, of course!)

Andrea Alù’s group from the Department of Electrical and Computer Engineering of the University of Texas at Austin signed an interesting article on a recent issue of the ACS journal Nano, where they claimed that  a graphene monolayer can be deposited over a surface in order to cloak  planar and cylindrical objects. Of course this is not the realization of the dream of the invisibility in the visible light range. In fact the cloaking works in the far-infrared and terahertz (THz) regime, and the principle of operation is that of the mantle cloak. Following this principle, it is possible to tune the surface impedance in such a way that the scattering from the object is largely reduced. This is very similar to the electrical concept found in the transmission line theory, where when you transmit a signal along a line you have no reflected signal when at the end of the line you have a matching impedance. One field of application could be, for example,  cloaked IR sensors, which may detect the IR signal (i.e. THz range) with no scattering.
Some more information about optical invisibility, distinct from the electromagnetic invisibility I talked above: the invisibility is that phenomenon where light rays deflect when they income over the object, and then they rejoin at the back of the same object. Invisibility in the visible light range  has been obtained by two distinct research groups under suitable conditions, with polarized light and in a high-refractive medium. In 1964 Russian physicist Victor Veselago proposed his theory on negative refractive index where light is deviated in “wrong way” and in 2000 this metamaterial was realized by Professor Sir John Pendry and colleagues from Imperial College and the University of California at San Diego. It has been demonstrated that negative refractive index metamaterials can be used to conceal objects. However until now invisibility has been obtained only for small objects under very constrained conditions.

In the movie invisibility led to mental instability


About Francesco Buonocore

Francesco Buonocore is an Italian solid state theoretical physicist, staff scientist of the Italian government agency ENEA. Francesco likes Physics, thinking about Physics and how Physics and life are related.
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