Tapered rib waveguides: fast and accurate finite difference beam propagation method.

A novel implementation of the finite difference beam propagation method (FD BPM) for optical rib waveguide structures in air is presented. Calculations for typical gallium arsenide based rib waveguide tapers confirm that the new approach is faster and requires less memory than previously used techniques, whilst maintaining accuracy. This is achieved by incorporating known analytical behaviour into a direct numerical algorithm.