We propose a novel design of integrated polarization splitter/combiner with ultra wide bandwidth. The proposed design utilizes the electro-optic (Pockels) effect in GaAs for splitting the polarizations. It also exploits the self imaging phenomenon in MMI couplers with a parabolic index distribution in the vertical direction to significantly increase the bandwidth. We also propose a novel approach for design optimization of the proposed structure. This approach is capable of extracting the propagation constants and their gradient with respect to all the design parameters. This allows for using gradient-based optimization. The computational time of this optimization procedure is only a fraction of that for other recently proposed approaches.
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