Directional beaming of surface plasmon polaritons from a metallic nanochannels with defected surface cavity

Abstract

In this paper, the directional excitation of surface plasmon polarities (SPPs) was investigated with numerical simulations in two plasmonic structures based on the metallic nanochannels with bumps. The simulation of SPPs and directional propagating fields on the output interface was carried out by employing a finite element method implemented by COMSOL Multiphysics. By analyzing behavior of the instantaneous electric field and power flow, the introduction of dielectric‐metal (DM) bumps produced an enhancement of the directionality and confinement of the output field in comparison with the case of metallic bumps. Since the DM bumps can form the vertical MDM Fabry‐Pérot (FP) cavity modes which are coupling with FP surface cavity modes between two bumps. The simulation results show that the optimized FP cavity length, dielectric thickness of layer in DM bumps and dielectric thickness of the layer between two bumps is crucial for the enhancement of the directional beaming effects. It is hoped that these outcomes can be used in several potential applications such as directional coupler (generator), plasmonic circuits, and nanoresolution optical beaming.