Study of optical silicon waveguide coupler

Abstract

Efficient light coupling between an optical fiber and a SOI waveguide is a hot topic in silicon optics field. The main challenge comes from the huge mismatch between the mode size of fiber and waveguide. We used simulation method to research the edge-based coupling from a single-mode optical fiber to a single-mode SOI (Silicon-On-Insulator) waveguide. To get the acceptable coupling efficiency, we used FDE (Finite Difference Eigenmode) solver and FDTD (Finite-Difference Time-Domain) simulation to calculate the optimal coupler size. The simulation result shows that coupling efficiency of 82% is achieved at a wavelength of 1550 nm and NA = 0.4, and coupling efficiency of 80% is achieved with a tolerance to fabrication error of 15 nm in etch depth.