Silicon Photonic Polarization Beam Splitter With Low Loss and High Extinction Ratio Enabled by TOPIC Bends

Abstract

We present a novel compact asymmetric bent directional coupler polarization beam splitter (PBS) fabricated on a silicon-on-insulator (SOI) platform using third-order polynomial interconnected circular (TOPIC) bends. The TOPIC bend design provides continuous curvature and curvature derivatives throughout the structure, which minimizes mode transition losses at connection interfaces. This approach allows for the implementation of tight bend radii to enhance extinction ratio performance without compromising insertion loss, thereby resolving the conventional trade-off limitation in bent-coupler PBS designs. The device performance was characterized through cascaded measurements involving up to 40 PBS units, with single-device loss parameters extracted via linear regression analysis. Comprehensive wafer-level testing across 61 dies confirmed excellent design reproducibility and manufacturing tolerance. The optimized PBS achieves insertion losses as low as 0.017 ± 0.007 dB for TE and 0.019 ± 0.018 dB for TM polarizations, accompanied by extinction ratios of 25.5 ± 0.5 dB and 29.6 ± 6.1 dB, respectively, at 1295 nm wavelength. These results establish new performance benchmarks for silicon photonic PBS devices and demonstrate significant potential for advanced polarization-handling applications in integrated photonic systems.