Sub-1 dB loss and polarization-insensitive O-band edge coupler for standard single-mode fiber on a 300 mm silicon photonics platform

With the growing demand for data center interconnects and high-performance computing, silicon photonics has emerged as a key technology for next-generation optical communication and interconnect systems. However, efficient coupling between silicon photonic chips and standard single-mode fibers remains a critical challenge limiting large-scale deployment. In this work, we demonstrate a sub-decibel loss, polarization-insensitive O-band edge coupler fabricated on a 300 mm silicon photonics active platform with two-layer silicon nitrides. The edge coupler employs a cantilever-based structure with a structurally optimized silica waveguide facet, significantly improving mode field overlap and alignment tolerance with standard single-mode fibers. Direct coupling of the optical field into a single-mode silicon nitride waveguide achieves excellent performance, with TE/TM mode insertion losses below 0.87 dB/1.0 dB and a polarization-dependent loss (PDL) below 0.14 dB across the 1260-1360 nm wavelength range. Furthermore, efficient interlayer coupling enables adiabatic optical field conversion from the silicon nitride waveguide to a single-mode silicon waveguide, maintaining high performance over a 100 nm bandwidth with TE/TM mode coupling losses below 0.85 dB/1.2 dB and a PDL below 0.37 dB. The device also exhibits excellent alignment tolerances in all three dimensions (horizontal, vertical, and coupling gap). This research provides a scalable and cost-effective solution for realizing high-performance optical input/output interfaces on advanced silicon photonics platforms, paving the way for large-scale integration in high-density optical interconnects and computing systems.