▎ 摘　　要

The propagation of surface plasmon polariton (SPP) wave can be controlled by tunable graphene conductivity via electrostatic gating and/or chemical doping. Here, we propose an alternative way to manipulate the SPP waves efficiently by designing the thickness of dielectric cladding on the graphene. Meanwhile, the SPP wave properties can be changed gradually rather than abruptly through designing the topology of cladding. Compared to the traditional method, the proposed approach is more convenient for machining with lower scattering loss. A plasmonic Luneburg lens has been realized using this method, which opens a useful way to achieve the planar plasmonic devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729557]