Study on transformation-based invisibility cloaks

[摘要] (cont.) It is seen that a square root transformation which forces the waves to be guided close to the outer boundary is more invisible than those generated by either linear or quadratic transformation. Simplified cylindrical cloaks may produce a larger scattering at nonnormal incidences than that from an object without any cloak. In addition, we suggest using a small number of homogeneous and anisotropic metamaterial layers to construct a practical cloak with satisfying performance with normal incidence and oblique incidence. Genetic algorithm was used to optimize the practical multi-layer structures. It is shown that using an optimized 4-layer cloak, the normalized scattering cross section from a perfect electric conductor cylinder can be reduced from 2.19 to 0.0039 with normal incidence. Another optimized 4-layer cloak working for the incidence of 30° is shown able to reduce the scattering cross section from 1.175 to 0.013. The latter cloak exhibits reduce scattering over a large range of incidence angles.

[发布机构] Massachusetts Institute of Technology