Numerical scrutiny of a silica-titania-based reverse rib waveguide with vertical and rounded sidewalls

In this work, a modal analysis of reverse rib waveguide (RRW) structures based on a silica-titania platform is carried out. The silica-titania waveguide films can be deposited via the sol-gel method and dip-coating technique. To combine this low-cost deposition technique with the economical fabrication method, we propose to structure the samples via wet-chemical etching. Due to the isotropic nature of wet etching, the waveguide architecture with rounded sidewalls is considered to model the RRW. Additionally, the modal conditions and bending loss are compared with the RRW with vertical sidewalls. It is assumed that this study will be beneficial for comprehending the modal conditions of waveguide structures with perfectly vertical and rounded sidewalls.