Miniature invisibility ‘carpet cloak’ conceals larger area
April 20, 2011
Physicists from the Technical University of Denmark (DTU), the University of Birmingham, UK, and Imperial College London, have developed invisibility “carpet cloaks” using metamaterials that can optically conceal a much larger area than other cloaking techniques of comparable size.
The team created an alternating-layer structure on a silicon-on-insulator (SOI) platform. Grating structures, a series of slits or openings that redirect a beam of light, channel light of a particular wavelength around an object. The cloak is made exclusively of dielectric materials, which are highly transparent to infrared light, so the cloak itself is very efficient and absorbs a negligible fraction of energy.
By precisely restoring the path of the reflecting wave from the surface, the cloak creates an illusion of a flat plane for a triangular bump on the surface. This hides its presence over near-infrared wavelengths ranging from 1480 nm to 1580 nm.
“Although our experiment was carried out at near-infrared frequencies, this design strategy is applicable in other frequency ranges,” notes Jingjing Zhang. “We anticipate that with more precise fabrication, our technique should also yield a true invisibility carpet that works in the microwave and visible parts of the spectrum and at a larger size — showing promise for many futuristic defense and other applications.”
Ref.: Jingjing Zhang et al., Homogeneous optical cloak constructed with uniform layered structures, Optics Express, April 19, 2011