Negative index growth in germanium-free nitrogen-doped planar SiO_2 waveguides

摘要

We have presented the growth of the average refractive index change and the refractive index modulation in germanium-free nitrogen-doped planar silica waveguides. No positive refractive index change could be observed indicating the absence of a type I grating. This also explaines the monotonous growth of the refractive index modulation. We could not observe a change in birefringence in the SiON waveguides induced by the UV exposure. This leads to the conclusion that UV-induced dilation or compaction is not the dominant mechanism causing the refractive index changes.