Pade/spl acute/ boundary conditions for the finite-element modeling of arbitrary planar junctions

Novel boundary conditions based on Pade/spl acute/ approximations for the frequency domain two-dimensional/finite element (2-D/FE) simulation of planar optical junctions of arbitrary geometry and number of accessing waveguides are presented and described in detail. This efficient formulation is straightforwardly implemented within the 2-D/FE framework and also can easily be used in finite difference schemes. Three examples show the applicability and reliability of the present method: a waveguide step discontinuity, waveguide transverse displacement and T-shaped beam splitter.