Out-of-plane scattering in optical waveguides

Measurements were made of the light scattered out of the plane of optical waveguides sputtered onto substrates of thermally oxidized silcon. The angular distribution of the scattered light can be explained theoretically as having as its origin roughness at the waveguide-air- interface. For waveguides of very high intensity scatter, the patterns are consistent with classical Mie scattering by spherical particles. This type of measurement may be useful in determining optimum conditions for fabricating very low-loss waveguide.