Moulding the flow of surface plasmons using conformal and quasiconformal mappings

In this paper, we analyze how transformation optics recipes can be applied to control the flow of surface plasmons on metal-dielectric interfaces. We study in detail five different examples: a cylindrical cloak, a beam shifter, a right-angle bend, a lens and a ground-plane cloak. First, we demonstrate that only the modification of the electric permittivity and magnetic permeability in the dielectric side can lead to almost perfect functionalities for surface plasmons. We also show that, thanks to the quasi two-dimensional (2D) character of surface plasmons and their inherent polarization, applying conformal and quasiconformal mapping techniques allows one to design plasmonic devices in which only the isotropic refractive index of the dielectric film needs to be engineered.