Optimized Design and Simulation of a Compact TFLN-Based Integrated Device for Simultaneous Polarizing and Equal-Power Beam Splitting

We present a compact thin-film lithium niobate integrated device simultaneously achieving high polarization extinction ratio and equal-power beam splitting, using two optimized oppositely-tapered graded-slope mode converters monolithically integrated with a multimode interference coupler. The converter's geometric profile is designed through a developed analytical method that evaluates local mode conversion efficiency, enabling flexible geometry customization for diverse applications. Based on this analytical method, the performance simulations and optimization are presented. The proposed integrated device's high extinction ratio, broad bandwidth, and fabrication tolerance show particular promise for precision optical sensing applications including fiber-optic gyroscopes.