A unified approach to coupled-mode phenomena

摘要

A unified approach is presented for the treatment of variousncoupled-mode phenomena in two parallel waveguides. This approach isnsummarized in a set of four coupled equations, which is derived directlynfrom Maxwell's equations. The equations are further simplified whennapplied to special cases such as evanescent coupling andngrating-assisted coupling between parallel waveguides [e.g., reduced tona set of two equations]. In particular, for evanescently couplednwaveguides, the equations reduce to the familiar vectorial coupled-modenequations. For grating-assisted waveguides the equations agree withnearlier treatments, although, in some cases, may include extra termsnwhich were omitted previously. Considering the special case ofnperturbations in a single waveguide, the equations in the examplesncoincide with those given elsewhere in earlier works. The reduction tonscalar equations or extension to multiwaveguide systems isnstraightforward