Ultra-broadband and compact TM-pass polarizer based on silicon nitride-assisted lithium niobate on insulator platform

An ultra-broadband and compact TM-pass polarizer is proposed based on the silicon nitride-assisted lithium niobate on insulator platform. By adopting width-tapered waveguide structures and a precisely engineered narrow waveguide section, selective polarization transmission is achieved. Simulations show an insertion loss of 0.04 dB and an extinction ratio of 42.7 dB at 1550 nm. Over the wavelength range of 1400-1920nm, the insertion loss remains below 0.42 dB and the extinction ratio exceeds 22 dB. The device achieves an ultra-wide operating bandwidth of 520 nm within a compact footprint of only 24 μm, while demonstrating robust fabrication tolerance.