Correlation between photodarkening and index change during 193 nm irradiation of germanosilicate and phosphosilicate fibers

Photodarkening at visible wavelengths and index changes are simultaneously studied as germanosilicate or phosphosilicate fiber is irradiated with 193 nm light. Using a modal interferometer, the relaxation of the photodarkening is shown to occur on a different timescale to relaxation of the index change. Spectral attenuation profiles are used to distinguish the relationship between index change and photodarkening due to both electronic absorption and Rayleigh scattering. The role of hydrogen on both processes is also studied.