Compact 90° trench-based splitter for silicon-on-insulator rib waveguides

Compact silicon-on-insulator (SOI) rib waveguide 90 degrees splitters based on narrow, high-aspect ratio (~10:1) trenches are designed and experimentally demonstrated. The splitter area is only 11 mum x 11 mum. Splitter optical performance is investigated as a function of both trench width and refractive index of the trench fill material. We examine three trench fill materials, air (n=1.0), SU8 (n=1.57), and index matching fluid (n=1.733), and find good agreement between experimental measurement and three dimensional (3D) finite difference time domain (FDTD) simulation. A splitting ratio of 49/51 (reflection/transmission) is measured for an index fluid-filled trench 82nm wide.