A new technique has enabled us to resolve the strong UV absorption spectrum in UV-exposed germanosilicate preforms. Our results show, for the first time to our knowledge, that the large photoinduced absorption changes between 165 and 300 nm (~700 dB/mm at 195 nm has been observed) can account for, ~3 ×10-4 of index change at 1.5 µm. The thermal-annealing dynamics of the photoinduced absorption changes also resemble those of fiber gratings, evidence that the color-center model of photosensitivity plays an important role in the photoinduced index changes in UV-written fiber gratings. We also find that the photoinduced absorption changes depend linearly on germania (i.e., germanium dioxide) concentrations in the preforms, and their exposure-time dependence can be fitted with a stretched-exponential function.
© 1995 Optical Society of America
L. Dong, J. L. Archambault, L. Reekie, P. St. J. Russell, and D. N. Payne, "Photoinduced absorption change in germanosilicate preforms: evidence for the color-center model of photosensitivity," Appl. Opt. 34, 3436-3440 (1995)