Scattering loss measurements of evaporated slab waveguides of SiO₂ and NdF₃ using a prism coupler and angle-limited integrated scattering

A method for finding the attenuation coefficient of a planar or channel waveguide is described. Results for SiO₂ and NdF₃ waveguides were obtained, showing that the latter presents better attenuation characteristics. The influence of the prism shape on the measurements was also tested and found to result in variations in the measured attenuation coefficient. Two different locations of the waveguides were selected for the coupling, and again variations occurred, suggesting irregular thickness of the thin films. The method uses concepts based on the angle-limited integrated scattering technique and also on the well-known prism coupling method. It may be possible to make the system fully automatic.