Modified finite-difference formula for semivectorial H-field solutions of optical waveguides

The propagation constants of rib waveguides are analyzed by the imaginary distance beam-propagation method based on a newly derived finite-difference formula for semivectorial H-fields. The formula ensures a truncation error of O(/spl Delta/x)/sup 2/, provided that the discontinuity lies midway between two mesh points. Comparison with previously published results for a rib waveguide as a classical benchmark shows the effectiveness of the present method.