Analysis of multilayer semiconductor rib waveguides with high refractive index substrates

The waveguiding properties of semiconductor rib waveguides with high refractive index substates are studied using the spectral index method. The propagation constants of leaky modes in such two-dimensional structures are calculated for the first time. The method is applied to the design of high wall GaAs-AlGaAs rib waveguides. Results indicate that the number of low-loss modes can be controlled by careful positioning of the substrate relative to the guiding region.