Archive for July 2015
The trouble with your standard present-day “invisibility cloaks” is that they’re not all that cloaky: kinda thick and inflexible, in fact. But wait:
Researchers at the University of California, San Diego, designed a carpet cloak, a device that covers an object and scatters light as if it’s hitting a flat surface instead of something three-dimensional.
The cloak is very thin only about a tenth the size of the wavelength of the photons it’s scattering and lossless, so there’s no dimming to give away the presence of the cloak. The scientists achieved this by using a new design and different materials. Instead of a periodic structure of metal, which absorbs light, they use two dielectric materials, a Teflon substrate studded with cylinders made of a ceramic. The ceramic has a high refractive index, and the Teflon has a low refractive index. When combined, they create a metamaterial, capable of bending light in unusual ways.
The finished product will of necessity be extremely thin:
It was designed for the microwave range, with a 0.6 cm thickness to handle 6 cm wavelengths, simply because those larger dimensions made it easier to work with. A cloak could be made for visible light but would have to be much thinner. Because the shortest wavelength the human eye perceives is slightly less than 400 nm, a cloak would have to be less than 40 nm thick, a dimension easily achievable by the photolithography processes used for making computer chips.