Structure related beam propagation

The general theory of a class of structure related (SR) non-orthogonal coor dinate systems is introduced for the first time. Special cases of this type of coordinate system used separately or in combination can automatically f ollow the local geometry of many common optical waveguide designs, thereby facilitating the fast and accurate simulation of photonic circuits, when in corporated within a FD-BPM algorithm. Substantial savings in run time and m emory are possible in comparison with standard FD-BPM in rectangular coordi nates.