Analysis of forward wide-angle light propagation in semiconductor rib waveguides and integrated-optic structures

Abstract

We analyse longitudinally varying semiconductor rib waveguides with a new nonparaxial wide-angle equation for unidirectional light propagation. We further develop a solution method involving multiplication of the incoming electric field by a series of unitary operators which are evaluated by splitstep fast Fourier transform and finite difference techniques. In the test case of a strongly guiding rib waveguide Yjunction, the estimated losses nearly coincide with those of standard Fresnel equation procedures. We also present a numerical analysis of an integrated-optic lens, demonstrating significant errors in previous results. Finally, we explicitly illustrate the increased accuracy of our new method in comparison to the Fresnel equation for a highly nonparaxial Gaussian beam.