RIGOROUS EFFECTIVE INDEX METHOD FOR SEMICONDUCTOR RIB WAVE-GUIDES

A saddle point variational principle, for estimating the propagation constant of an optical rib waveguide mode from a discontinuous trial function, is generalised to provide a theoretical underpinning for the familiar effective index method. It is shown that better accuracy can be achieved in a rigorous manner, while maintaining much of the simplicity that makes the original effective index approach so attractive.