Modal dispersion and attenuation measurements of silicon nitride and silicon oxynitride waveguides using a streak camera

By measuring short pulse propagation in silicon nitride and oxynitride waveguides fabricated on silicon, it has been possible to characterize both attenuation and group velocity dispersion accurately for the different modes that propagate. The method is self-calibrating, using the ratio between scattered light from forward and backward traveling pulses at a particular point on the waveguide. In principle, the group velocity data can be used to calculate the phase velocities for the different modes using known dispersion relations. The phase velocities were measured independently using a prism coupling technique, and the group velocities that could be derived from them matched the experimental data within a few percent. The resolution of the technique is limited mainly by amplitude fluctuations of the laser. The full-width-half-maximum resolution was at best about 12 ps but should be extendable to better than 5 ps