The Continuing Role of Beam Propagation Methods in Photonics Design

Significant attention and investment has been made in providing computer simulation packages for photonics devices and systems. Techniques must typically not only provide accurate vector results, or at least a reliable error estimate, but also be able to deal with multi-physics, multi-scale problems, intricate materials properties and arbitrary geometries. Time domain numerical techniques such as FDTD and TTM have come to the forefront in recent years, driven by their flexibility, adaptability and compatibility with parallel computing techniques. Nevertheless much present day simulation and design work still involves approximations and an automated all- in-one design tool suitable for every purpose is far from realization. Beam propagation methods (BPMs) have proved an invaluable tool for the designers of integrated photonics in the last decades. Many of the original underlying assumptions have been relaxed using new formulations and algorithms. In this invited paper we will show that the computational efficiency of BPMs means they still have much to offer, whilst highlighting some residual issues.