Design of Nanoring Resonators Made of Metal-insulator-metal Nanostrip Waveguides

We report on the design of nanoring resonators made of metal-insulator-metal (MIM) nanostrip waveguides. The characteristics of the lightwave propagation through the silver-based MIM plasmonic waveguides with an air superstrate are examined. The effective refractive indices, the propagation losses, the bending losses, and the beat lengths are analyzed by using 2D and 3D finite element methods (FEMs). For the optimization of the nanoring resonators, we examined the resonant mode power and the Q factor with respect to the width of the MIM nanostrip and the separation between the ring resonator and the straight waveguide. We obtained an optimized nanoring resonator that had submicron diameters (R = 399 nin) and 3(rd)-order resonances at a 1550-nm wavelength. These nanoring resonators will play an important role as the basic building blocks for the realization of nanoscale photonic integrated circuits.