In this paper, outlines of the derivation of two recently developed finite
difference beam propagation methods based on the higher-order Fade approxim
ations are given to simulate the optical field propagation of tilted and tu
rning waveguides. In order to investigate the accuracy and limitation for a
propagation angle of these approaches, numerical results are presented for
two benchmark tests. The present algorithms will offer, to our knowledge,
the new beam propagation methods in optics.