A UNIFIED APPROACH TO COUPLED-MODE PHENOMENA

A unified approach is presented for the treatment of various coupled-m ode phenomena in two parallel waveguides, This approach is summarized in a set of four coupled equations [see (8) or (12) in the paper], whi ch is derived directly from Maxwell's equations. The equations are fur ther simplified when applied to special cases such as evanescent coupl ing and grating-assisted coupling between parallel waveguides [e.g., r educed to a set of two equations], In particular, for evanescently cou pled waveguides, the equations reduce to the familiar vectorial couple d-mode equations. For grating-assisted waveguides the equations agree with earlier treatments, although, in some cases, may include extra te rms which were omitted previously. Considering the special case of per turbations in a single waveguide, the equations in the examples coinci de with those given elsewhere in earlier works. The reduction to scala r equations or extension to multiwaveguide systems is straightforward.