Multiple coupled waveguide switches using alternating Δβ phase mismatch

A design using alternating sections of dephasing to improve the transfer characteristics in multiple waveguide couplers is proposed. This is an extension of the Δβ coupler principle introduced by Kogelnik and Schmidt. The structure permits tuning with an applied voltage via the electrooptic effect. Adjustment of the electrode voltage can also compensate for fabrication imperfections in coupling lengths. The principle can be applied to both types of operation of the multiple waveguide coupler: (i) transfer of a signal between outermost guides, and (ii) transfer of a signal from the center guide symmetrically to an excitation of the two outermost guides. The three-waveguide Δβ coupler will be described in detail, and the results will be presented for arbitrary Nth order systems.