The design of an NxN multi-mode interference coupler with weakly guiding condition is considered. Focus is put on the positioning of access waveguides. The best positions are obtained using eigenvectors overlapping requiring only a modal solver leading to a very short computation time as no propagation is required. Beyond its simplicity, it provides a clear physical understanding of the self-image theory when the multi-mode section is weakly guiding. This method computes in addition the tolerance on the access guide positioning. Results are in excellent agreement with those from literature.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
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