A new iterative bidirectional beam propagation method

A new bidirectional beam propagation method is developed for numerical simulation of wave-guiding structures with multiple longitudinal reflecting interfaces. It is an iterative method that works on the wave field components directly. Operator rational approximations developed in the one-way beam propagation method are used together with a modern Krylov subspace iterative method. Compared with earlier bidirectional beam propagation methods based on the transfer matrix formulation, the new method is numerically stable and models evanescent modes better.