Compact Bend-Less Mach-Zehnder Interferometer on Barium Titanate for Programmable Photonics

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This work presents the design of a compact, bend-less Mach-Zehnder Interferometer (MZI) for high-density programmable photonic circuits, utilizing ferroelectric barium titanate (BaTiO3 or BTO) as the electro-optically active material. Unlike the conventional MZI, which uses waveguide bends to isolate or decouple waveguides in the phase shifter section, the proposed design removes the need for bends by introducing a controlled mode mismatch between the waveguides. We utilize one of the high Pockels coefficients of BTO (r<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">33</inf> = 342 pm/V) at a low voltage of 4.5 V to realize the required mode mismatch for decoupling waveguides in the phase shifter. Full-vector 3D COMSOL simulations are performed for the complete design using a push-pull configuration in the phase shifter, resulting in a low V<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</inf> • L product of 0.276 V • cm.