ANALYSIS OF RIB WAVE-GUIDES AND COUPLERS BY THE PROPAGATING BEAM METHOD

The propagating beam method (PBM) is known to be an accurate tool for modeling propagation in waveguides with graded-index profiles. Intuition suggests, on the other hand, that the PBM is inappropriate for waveguides such as rib waveguides that exhibit refractive-index discontinuities. We demonstrate here that the PBM is indeed applicable to rib waveguides, although extremely small longitudinal integration steps may be required. Comparison with other numerical methods for calculating mode indices for single waveguides shows good agreement. The assessment of accuracy for modeling rib-waveguide directional couplers, on the other hand, is less certain because of a general lack of consistency among the various methods used in the comparison. © 1990 Optical Society of America.