Large UV-induced negative index changes in germanium-free nitrogen-doped planar SiO₂ waveguides

Negative refractive index changes of up to 1.7 ×10-3 have been induced by 248 nm excimer laser light in planar germanium-free SiON waveguides. Highly temperature-stable 4OdB Bragg gratings with a length of 8mm have been written. A novel mechanism of photosensitisation was used to create the high-index changes.