Large cross section Y-branch with new fiber-waveguide endface in silicon-on-insulator

In this letter, large cross section Y-branches with new fiber-waveguide endface were etched by inductively coupled plasma reactive ion etching on silicon-on-insulator (SOI) wafer. The near-field image shows that the Y-branch works well. HfO₂ films were deposited onto the waveguide endface by the electron beam evaporation method. The waveguide endface root mean square roughness was approximately 13.3 nm measured by atomic force microscopy. The optical properties of HfO₂ films as single-layer antireflection coating on silicon substrate were investigated in detail. The results suggested HfO₂ film was a very attractive single-layer antireflection coating for SOI-based waveguide devices.