Study on the effective index of layered surface plasmon waveguides

The relationship between the effective index and the material and structural parameters of layered surface plasmon (SP) waveguides, including planar single interface and planar sandwich SP waveguides, is investigated and numerical simulation is carried out for an operating wavelength 1550 nm. The results show that in case of the single interface SP waveguide there is a finite maximum effective index for a certain dielectric permittivity. There is a finite maximum effective index as well for the symmetric guided mode of sandwich SP waveguide while the cladding layer permittivity is optimized; its upper maximum is the very maximum one of single interface SP waveguide and its lower limit is the refractive index of the cladding dielectric material.