Improved multistep method for wide-angle beam propagation

Abstract
To improve a wide-angle beam propagation method using a finite-difference technique, the generalized Douglas scheme for variable coefficients is applied to a multistep method. A truncation error of O(/spl Delta/x)/sup 4/ is achieved in the transverse direction. The effectiveness of the present method is demonstrated in the analysis of a tilted step-index slab waveguide.