Multifrequency cloak with multishell by using transformation medium

Abstract

We theoretically investigate multifrequency cloak based on multishell by using transformation medium. As for each shell, we use the Maxwell–Garnett theory and the spectral representation theory to design the permittivity profile for the transverse magnetic wave. The plasma frequencies of the metals used in the inner (B) and outer (C) shells must satisfy ω1<ωpC<ω2<ωpB. In such case, incident electromagnetic wave of lower frequency ω1 will be distorted only by the outer shell C without entering the inner shell B to achieve invisibility. However, at the higher operating frequency ω2, the outer shell C is transparent by choosing the materials appropriately, and the incident electromagnetic wave will be distorted only by the inner shell B to achieve invisibility. So, the multishell cloak can work simultaneously on two different optical frequencies. Furthermore, we use the anisotropic differential effective dipole theory to evaluate the efficiency of the cylindrical cloak.