Fibre-coupled high-index PECVD silicon-oxynitride waveguides on silicon

Abstract

The deposition of PECVD silicon-oxide (SiOx) and -oxynitride (SiOxNy) for fabrication of planar waveguides with small bending radii is investigated. The focus is on fabricating homogeneous and during annealing non-cracking core layers. Therefore, the stress behaviour and the hydrogen content are examined. It is shown that a stress-free cover layer can be achieved by adjusting the as-deposited stress and the annealing process. High numerical aperture (NA) waveguides with small bending radii are fabricated. A low-loss coupling between waveguide and fiber is achieved by using special high-NA fibre. Their mode field diameter fits very well to the waveguides. Low-loss splicing to standard transmission fibres is optimized.