Aperture-coupled MIM plasmonic ring resonators with sub-diffraction modal volumes.

We propose and investigate ultracompact aperture-coupled plasmonic ring resonators with submicron bending radii based on strongly-confined metal-insulator-metal plasmonic waveguides. Enhanced coupling can be obtained via diffraction by small apertures having typical widths between 50-100 nm in the metallic sidewall between the ring and bus waveguides. Both analytical model and rigorous FDTD simulations show that 500 nm-radius ring resonators can be obtained with low insertion loss, wide free spectral range and sub-diffraction cavity volume of less than 0.1(lambda(0)/n(eff))(3).