Numerical Analysis on the Multilayer Nanoring Waveguide Pair

We propose a multilayer nanoring waveguide pair and investigate the surface plasmon modes and gap field enhancement between the two multilayer nanoring waveguides. Due to the strongly coupled electric fields between multilayer nanoring waveguides, a field enhancement contrast ratio over 10
⁸
can be obtained. The mode refractive indices and the propagation lengths are analyzed by the commercial software COMSOL Multiphysics. We also demonstrate the influences of varied structure parameters on gap field enhancement. Moreover, graphene is replaced by gold in the multilayer nanoring waveguide pair to discuss the properties change. Thanks to the tunable surface conductivity, the gap field enhancement can be controlled by adjusting the chemical potentials of graphene. The application of multilayer nanoring waveguide pair may have a great prospect in photoelectric devices and bio-sensing.bio-sensing.