Mode conversion in asymmetric dielectric/metal/dielectric plasmonic waveguide using grating coupler

Conversion of surface plasmon polaritons (SPPs) between the upper and under interfaces of an asymmetric dielectric/metal/dielectric (DMD) waveguide using a grating coupler has been investigated. The coupling efficiency of the under mode and the upper mode has been discussed. Various optical and geometrical parameters of the grating structure have been studied in detail and the related physical origins have been illustrated. Based on the Fabry–Perot resonance condition, a maximum coupling efficiency of more than 18% has been obtained at the optical communication wavelength, which could be devoted to the converter between the two modes for utilizing their respective specialty in plasmonic circuitry.