Simplified theoretical model for surface plasmon excitation in D-shaped fiber

This paper presents a simpler approach for the analysis of the excitation and the mode coupling effects of surface plasmons in a D-shaped fiber. It is proposed the resonant transfer of energy in the fiber can be predicted by considering the coincident propagation constant for two distinct waveguides, namely a circular step-index fiber; and a multilayered step-index planar waveguide having refractive indices assuming those of the core, cladding, metal film and the outer dielectric. The point of coupling is observed to be the intersection of the dispersion curves for the surface plasmon modes and the circular fiber mode. The theoretical results are in good agreement with numerical simulation results of the D-shaped fiber obtained using Finite Element Method based software.