Beam propagation method tailored for step-index waveguides

We present a scalar beam propagation method (BPM) that is tailored for step-index waveguides. For many structures, especially periodic ones such as star couplers, it is many times faster than and avoids the spatial quantization of existing BPMs. It can handle large propagation angles but not very large effective index steps and does not perfectly preserve energy. We provide the two-dimensional version in C-language code.