The beam propagation method (BPM), originally derived from the paraxial (Fresnel) approximation, has been widely used to study optoelectronics devices. The paraxial limitation was removed in the so called wide-angle beam propagation methods (WA-BPMs). Here WA-BPM focus on extending the range of applicable “angle” using high order Padé approximation in the transverse direction. Such extensions are invaluable not only for the simulation of propagation at large angles to the axis but also because they allow accurate propagation through regions whose refractive index may differ greatly from the input reference index [19] – [22].