2D broadband invisibility-cloak array works in the visible spectral region

In an arXiv preprint, researchers at Towson University (Towson, MD) and the University of Maryland (College Park, MD) describe their fabrication of large arrays of small 2D broadband invisibility cloaks that operate in the visible spectral region; the array could find application in sensing and communications.

The arrays are created by coating a commercially available microlens array on the lens side with a 30 nm gold film and pressing it against a flat glass slide also coated with a 30 nm gold film. The result is an array of adiabatically tapered gaps between the two gold films (the gap between a sphere and a plane surfaceproduces broadband cloaking, with cloaked areas for different wavelengths nested within one another). Laser light at 514 nm along with a 500 μm square array period produced cloaking of about 20% of the surface area. Light at 514 and 488 nm, along with a smaller period of 30 μm in a hexagonal arrangement, demonstrated broadband cloaking, but the hexagonal geometry produced enhanced light scattering in directions other than the symmetry axes. See preprint arXiv:1204.2319v1 [physics.optics].