Finite element study of metal-corner plasmon polariton waveguides

Surface plasmon poalriton (SPP) waveguides have the potential to bring technology revolutions in fields like photonic integration, optical sensing, and even deep sub-wavelength imaging. The peculiar guidance mechanism of such waveguides however imposes great challenges on our existing theoretical modeling tools. In this paper, the superiority of finite element method (FEM) is examined for deriving modes guided by realistic SPP waveguides. In consideration of the anisotropic field profiles of most SPP waveguides, we propose the deployment of anisotropic finite element mesh. The anisotropic finite mesh is found to be able to reduce the numerical problem size greatly. Among all SPP waveguides, we emphasis the importance of the metal-corner waveguides, including both V-channel and A-wedge waveguides. Such metal corners can be found in most SPP waveguides proposed or fabricated so far. The properties like dispersion and propagation loss etc are studied by using FEM. Subwavelength light guidance can be achieved by such corner waveguides when their angles are kept small enough. However their applicability in nanoscaled optical circuits is affected by high propagation loss. Loss reduction or introduction of metamaterial with gain is desired in order to obtain small mode field size as well as low loss.