Inverse method for designing external cloak based on Laplace´s equation

The external cloak is a special device that can make an object outside the cloaking shell invisible. In this paper, the inverse method based on numerical solution of Laplace´s equation is applied to design arbitrary shape external cloak, without any knowledge of the coordinate transformation. The performance of the cloak is verified by full-wave simulation. The design method is extended to three dimensional case, which greatly enhances the applicability of external cloak.