In DepthOptics

Skintight invisibility cloak radiates deception

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Science  18 Sep 2015:
Vol. 349, Issue 6254, pp. 1269
DOI: 10.1126/science.349.6254.1269

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In J. K. Rowling's blockbuster novel Harry Potter and the Philosopher's Stone, the young wizard Harry receives an invisibility cloak: a silky garment that makes him disappear. Now, researchers in the budding field of invisibility cloaking have made an ultrathin cloak of their own. It won't hide Harry; it conceals objects just a few micrometers in size. But compared with earlier, bulkier cloaks, such a device might be more easily scaled up to hide larger things. The original invisibility cloaks smoothly funnel light or longer wavelength electromagnetic waves around an object so that it can't be seen. That means they must be thick compared with the wavelength of light and big compared with the object. In contrast, the new cloak changes light waves bouncing off an object on a surface to erase the distortions the object would otherwise imprint on the waves, effectively hiding the thing from view. To do that, the researchers apply a "metasurface"—a skintight layer of transparent insulator decorated with rectangles of gold of different sizes—that act like little antennas radiating in concert. To prove the "skin cloak" works, they built one to hide a landscape of micrometer-sized hills and valley and make it appear mirror flat.