In this paper, the Surface Plasmon Polariton (SPP) dispersion relation in the TM polarization for the plane interface between a homogeneous dielectric medium (with constant εd) and a gradedpermittivity (i.e. nonhomogeneous) plasmonic medium (with dielectric function εp(z)) is obtained where ‘z’ is normal coordinate to the interface. For small variation of εp(z) it is revealed […]