Guided Plasmon Modes of Elliptical Cross Section Silver Nanoridges

Propagating two-dimensional plasmon polariton modes guided by elliptical cross section silver nanoridges are investigated in this paper. Mode field profiles, dispersion curves, propagation distances, and figure-of-merits of the plasmon modes are calculated for various elliptical cross section silver nanoridges. It is found that the elliptical cross section metal nanoridge, if designed properly, can support a tightly confined plasmon mode with a longer propagation distance and a higher figure-of-merit than the flat-top nanoridge waveguide of the same width. The optimal nanoridge waveguide is obtained when the elliptical waveguide cross section becomes a semicircular cross section. When the curvature of the elliptical nanoridge is large, the nanoridge plasmon mode approaches the wedge plasmon mode.