Low-Loss and Compact Bends on Multi-Layer SiN-on-SOI Platform for Photonic Integrated Circuits

Low-loss, compact silicon nitride and silicon waveguide bends are demonstrated using COMS-compatible multi-layer PECVD SiN-on-SOI integration platform over the whole C band. The curvature of advanced waveguide bend is designed with linearly changing to reduce bending loss. The bending loss for PECVD SiN reduces from 0.087 dB/90° for normal bend to 0.037 dB/90° for advanced bend with the radius of 30 μm. It indicates a 60% footprint reduction with same loss level compared with the normal bend with 50- μm radius. Wafer-level distribution and uniformity of the bending loss are characterized, showing the stable performance. Similarly, we demonstrate a 3 μm-radius silicon waveguide bend in the same platform, showing the bending loss of only 0.0065 dB/90° bending loss, which is even smaller comparing to 0.012 dB/90° bend loss of a 5 μm-radius normal bend. Such advanced bend design with significantly reduced loss and footprint paves a way for high-dense large-scale photonic integrated circuits.