On approximate theories of single-mode rectangular waveguides

We present a new scheme of computation for the CEVAR (cosine-exponential field based variational method) for modelling wave propagation in single mode rectangular waveguides. The method avoids non-linear optimization. We show that the fully optimized weighted index approach is identical to the CEVAR method in which the Rayleigh quotient is optimized to obtain the best separable approximation to the field propagating in single mode guides with rectangular dimensions.