Cloaking at a distance from folded geometries in bipolar coordinates

We propose a kind of folded geometry in bipolar coordinates. Transformation optics in such folded geometries has many intriguing applications, such as a kind of conceptual devices that can exactly cancel the scattering of a prespecified external object and thereby make it invisible. Numerical simulations are performed to confirm the properties. (C) 2009 Optical Society of America