Wide-angle propagating beam analysis for circularly symmetric waveguides: comparison between FD-BPM and FD-TDM

The finite-difference beam-propagation method (FD-BPM) with a (1, 1) Pade approximant operator is formulated for circularly symmetric waveguides. A tapered step-index fiber is analyzed, and the computed field distribution is compared with that from the scalar finite-difference time-domain method (FD-TDM). The present method offers improvement in the evaluation of a radiation-mode field compared with the conventional FD-BPM based on the paraxial approximation.