A scalar coupled-mode theory with vector correction

A coupled-mode formulation based on scalar modes is developed for guided-wave devices in optoelectronics and fiber optics. In the formulation, the vector property of the electromagnetic field is represented as additional coupling to the coupling due to the refractive-index perturbations. The nonorthogonality of the scalar modes in the individual waveguides is taken into account. The theory is applied to directional couplers made of parallel slabs, rectangular channel waveguides, and circular fibers. Comparisons with the exact solutions available demonstrate very good agreement. Within the framework of the simple scalar analysis, the theory may be applied to the modeling and analysis of propagation and coupling of the vector electromagnetic waves in a broad range of practical optical guided-wave devices.<>