Plasmonic multimode waveguides with transversely structured core.

We analyze the propagation of surface plasmons in metallic multimode waveguides that consist of alternating stripes of different metals in the transverse direction and that are homogeneous in the longitudinal direction. The purpose of structuring the waveguide in the transverse direction is to take advantage of the different attenuation and propagation constants for different metals. Here, in particular, alternating stripes of Ag and Au are considered. This allows one to influence the modal spectrum. We consider two different, well-defined waveguide configurations. For these, the propagating plasmonic modes are calculated. Based on the numerical simulations, we discuss the attenuation and propagation behavior and show the resulting eigenmodes for different values of the structural parameters, i.e., widths and thicknesses.