Surface plasmon polaritons locally excited on the ridges of metallic gratings

With the perspective to achieve an in-depth understanding of metallic periodic surfaces, we study the surface plasmon polaritons that are locally excited on the ridges (between the indentations) of metallic lamellar gratings composed of slits or grooves. An approximate model and fully vectorial computational results show that the normalized excitation rate is rather small for slit arrays (approximately 10 at maximum) and is surprisingly weakly dependent on the metal permittivity. Additionally, the analysis is supported by an intuitive microscopic model that shines new light on the role of surface plasmons in the transmission and resonance anomalies of periodic metallic surfaces.