Three-Dimensional Electromagnetic Simulation of Surface Plasmon Propagation Between Sub-Wavelength Hole-Pair on Metallic Thin Film

Abstract

Generation, penetration, and propagation of surface plasmon waves excited around a septal wall between a pair of sub-wavelength holes on a metallic thin film has been analyzed by a three-dimensional numerical simulation software COMSOL Multiphysics (COMSOL AB, Sweden) with RF module, which are based on finite element method. The analytical 3D-model consists of four layers of quartz, metal, vacuum, and perfect matched layer (PML), and the metallic layer has the pair of through holes at the central region. The holes or metallic layer is uniformly illuminated by a linearly-polarized plane wave of laser light comes from the glass layer. Focusing and enhancement of the surface plasmons at the rear side of metallic film or the end of septal wall have been studied by changing (1) spacing of holes, (2) laser wavelength, (3) laser polarization, and (3) material and (4) thickness of metallic thin film. A series of the numerical results will be presented and discussed as application of the localized light source to the apex of fiber probe used in scanning near-field optical microscopy.