Guided plasmon modes of triangular and inverted triangular cross-section silver nanoridges

Propagating plasmon modes guided along silver metal nanoridges with triangular and inverted triangular cross sections are investigated in this paper. Mode field profiles, dispersion curves, propagation distances, and figure-of-merits of the plasmon modes are calculated for silver nanoridges with various triangular and inverted triangular waveguide cross sections. It is found that the triangular cross-section nanoridge waveguide, if designed properly, can have longer propagation distance and higher figure-of-merit than the flat-top nanoridge waveguide of the same width. When the triangle height of the nanoridge is high, the mode approaches the small angle wedge mode. An inverted triangular cross-section nanoridge mode can be considered as a hybrid mode of two metal wedge plasmon modes. When inverted triangle depth increases, the propagation distance and the figure-of-merit decrease dramatically, suggesting poorer performance when compared to the flat-top nanoridge plasmon waveguide.