Observation of UV induced absorption changes in tellurite and selected doped silica glasses

With the advent of fiber Bragg gratings and integrated optics, photosensitivity and photoinduced refractive index changes in glasses have become an important area of study. Several glasses including compositions of Eu doped silicates, cerium doped silicates, and germanium doped silicates exhibit UV induced refractive index changes. Its reasonable to expect that many glass compositions will also show refractive index changes upon irradiation by a suitable wavelength. It has been suggested that refractive index changes observed in germanium doped silica are caused by large absorption changes in the ultra-violet spectrum through the Kramers-Kronig relationship. The Kramers-Kronig equations are two integrals over all frequencies that relate the real part of the complex refractive index to its imaginary part