Power exchange in strongly coupled diffused channel waveguide arrays: an analytical approach

We present the modified scalar coupled mode analysis for an array of N diffused channel waveguides. The study simulates the lateral evanescent field coupling in the graded index channel waveguide array. In a two-step procedure, the propagation characteristics of individual waveguides are obtained first by the completely analytical, closed-form expressions obtained from the variational method. Consequent upon obtaining the individual waveguide characteristics, the complete scalar coupled mode theory has been developed that includes the non-orthogonality of the individual waveguide modes for strongly coupled waveguides. The coupled mode equations are solved to obtain the supermodes corresponding to the coupled waveguide configuration. Further to this, power exchange in the graded index multi-waveguide systems has been studied. Complete power transfer between the outside guides of the symmetric three-waveguide graded index coupler is reported when the condition of equispaced effective indices is met.