Coupling between successive Ti:LiNbO_3 waveguide bends and branches

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Abstract
The splitting ratio of a single-mode waveguide structure consisting of a symmetric Y-branch preceded by an abrupt bend has been shown to depend on the bend-branch separation as a result of radiation field coupling. Ti:LiNbO3 channel-waveguide bend-branch structures with segments of various lengths connecting the bend and the branch were fabricated and tested. An equivalent slab-waveguide model of these structures was also analyzed numerically. Measured power-splitting ratios exhibit a strong oscillatory dopendence on the connecting-segment length and range from 0 to ±6 dB, with the oscillations becoming less pronounced at longer connecting-segment lengths. The power splitting also depends on the optical polarization and wavelength and the distribution of diffused titanium in the waveguide. Results of this study can be used to design compact multiple-branching structures.