Cloaking by reaction

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The demonstration of cloaking by reaction uses a metamaterial cylinder with dielectric constant close to -1, with a hole in its centre. This is placed in an external field, and a collection of polarizable dipoles is placed nearby. These may be arranged around the silhouette of a shape.

As a collection of dipoles approach the cloaking radius (the dashed circle), the cloaking cylinder reacts with the dipoles in such a way as to quench the external field near each of them. The collection of dipoles thus becomes invisible to the external field. This is translated in the images of the animation as the region within the silhouette becoming more and more transparent. One of the extraordinary features of cloaking by reaction is that the cloaking radius is given by the square root of the cube of the shell radius divided by the core radius. Thus, as the core radius diminishes, the cloaking region expands, in a fashion strangely reminiscent of homeopathy!

(from the article “L’invisibilité en vue” by S. Guenneau, S. Enoch, and R. C. McPhedran, submitted to Science et Vie).