Reduction of scattering using thin all-dielectric shells designed by stochastic optimizer

Adaptive differential evolution method has been used for optimization of all-dielectric multilayer coatings in order to reduce total scattering from spherical targets. The optimal refractive index profiles have been found for various sizes of targets and thicknesses of coatings. Few profile types that appear to be optimal for various geometrical parameters have been identified. Scattering of the target with diameter of 0.75 lambda has been reduced by 85% using 0.16 lambda thick coating formed by isotropic dielectric materials. For larger targets, scattering reduction becomes smaller, but it still reaches 50% for targets with the diameter of 1.5 lambda. The obtained designs provide a route to implement cloaking without the use of magnetic and anisotropic metamaterials. (C) 2014 AIP Publishing LLC.