Forward wide-angle light propagation in semiconductor rib waveguides.

We derive and examine a new nonparaxial wide-angle equation for unidirectional light propagation. We then develop a rapid unitary solution procedure utilizing both the split-step fast-Fourier-transform and finite-difference techniques. Our calculated losses for the test case of a strongly guiding semiconductor rib-waveguide Y junction are in good agreement with the results of Fresnel equation methods.