Wide angle oblique beam propagation

The properties of wide-angle beam propagation in oblique coordinate system are studied. The wide angle algorithm is compared with the standard paraxial one and with the beam propagation in the rectangular coordinate system. The results obtained by the new algorithm are consistent with the ones given by the standard rectangular Beam Propagation Method. It is found that when the local waveguide geometry does not match the local coordinate system used to describe it the wide-angle algorithm is sensitive to staircasing.