Modification of dispersion, localization, and attenuation of thin metal stripe symmetric surface plasmon-polariton modes by thin dielectric layers

Abstract

We systematically investigated the properties of the fundamental symmetric surface plasmon-polariton mode supported by a finite width gold microstripe with thin dielectric layers placed above and below it. This paper describes the dispersive behavior of the fundamental symmetric mode and the dependence of its attenuation and confinement on the thin dielectric layers’ thickness and refractive index. When the dielectric layers have a refractive index less than that of the cladding, the dispersion curve shifts toward the cladding light line and the mode attenuation is reduced with the tradeoff of reduced confinement. For dielectric layers with an index of refraction higher than that of the cladding, the dispersion curve shifts away from the cladding light line and the mode confinement is enhanced at the cost of increased attenuation. When designed properly, the higher refractive index dielectric layers in combination with the low index cladding can achieve tight mode confinement which cannot be obtained by using either a high or low index homogeneous dielectric cladding. The dependence of the mode’s properties on the thickness and width of the metal stripe and dielectric layers is also investigated.