Ultra-wideband dual-polarization silicon nitride power splitter based on modal engineered slot waveguides

Silicon nitride (SiN) waveguides provide a substantially lower index contrast, thermo-optic coefficient, and reduced birefringence compared to silicon-on-insulator waveguides. These properties make SiN a prominent candidate for implementation of ultra-wideband dual-polarization photonics circuits with a great potential for datacom applications. State-of-the-art SiN power splitters are still hampered in terms of either bandwidth or single-polarization operation. Here, we propose to overcome these limitations by exploiting modal and waveguide symmetry engineering in a single-mode slot waveguide. This topology prevents mode-beating, while granting symmetric power splitting for both polarizations. Experimental characterization of the fabricated device shows low loss ( $<0.62\mathrm{d}\mathrm{B}$ ) and imbalance ( $<0.6\mathrm{d}\mathrm{B}$ ) within an unprecedented bandwidth of 420 nm (1.26–1.68 µm).