Unequal multi-layered cloak with axial constitutive parameter spatially invariant

Constitutive parameters of the perfect cloak are always nonlinear, and require anisotropic material to realize in practice. In this paper, we have proposed practical approach to construct invisibility cloaks through layered structures with unequal thickness. One example, the cylindrical cloak with axial constitutive parameter spatially invariant, has been demonstrated. This cylindrical cloak was effectively constructed using eight concentric layers which are not equal thickness. Compared with cloak constructed through ten concentric layers of equal thickness, the advantages of using concentric layered structures with unequal thickness is that the performance is well keeping while the layers is reduced, so the realization of complexity is greatly reduced.