Fabrication tolerances of SOI based directional couplers and ring resonators

In this work the effect of deviations of the waveguide shape introduced by manufacturing tolerances on the performance of lateral directional couplers and ring resonators based on SOI-rib-waveguides are investigated by using Full Wave 3D Finite Element Method. Beside dimensional deviations like waveguide width and slab thickness for the first time the influence of waveguide sidewall angle and wet chemical cleaning procedures on the device performance are carefully analyzed. Efficient measures against systematic process tolerances are proposed and possible actions to improve device stability and reproducibility are discussed.