The optimized design for the illusion device is studied based on the genetic algorithm. For an electrically small target, a core-shell illusion device by optimizing the material and geometrical parameters of the covering shell can achieve the equivalent scattering, in which the monopolar and dipolar modes are dominant. With the increase of the device size, more scattering terms become obvious, and the ability of the single-layered shell to manipulate the scattering is very limited. For a target

more »

... with dimension compared with the wavelength, we construct a concentric multi-layered device made of isotropic and homogeneous materials. The full-wave simulations are carried out to demonstrate the illusion performance of the optimized multilayer. The physical explanation is given that all scattering modes of the multi-layered illusion device after optimization approach to that of the target.