Efficient and Simple Two-Dimensional Beam Propagation Method for Step-Index Waveguides

We present a two-dimensional scalar beam propagation method (BPM) that is optimized for step-index waveguides. From many structures, especially periodic ones, it is many times faster than and avoids the spatial quantization problem of existing BPMs. It can handle large propagation angles but not vary large effective index steps. We provide the full method in C-language code.