A new set of coupled mode equations are derived from Maxwell equations to investigate several types of mode coupling phenomena in the periodically perturbed dielectric waveguide for the case of oblique incidence.
It is found that our coupled mode equations for the TE-TE mode coupling can be reduced to the coupled mode equations derived from the singular perturbation method for the unbounded periodic dielectric waveguide.
Four types of mode couplings are analyzed and the coupling coefficients are calculated for the corrugated waveguide. Comparision with the results of Stegeman et al. shows that the obliquity factors are the major differences between the two results.
