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We demonstrate a similar wavelength-dependent response for both the generation of Ge E' centers and the formation of photosensitive gratings in germania-doped silica fibers. This supports a model for the grating formation whereby two-photon absorption of laser radiation into the UV bleachable absorption band of an oxygendeficient germania site creates hole traps, modeled as Ge E' centers, which are detectable with electron spin reasonance spectroscopy.

The effects of controlled atmosphere heat treatments on the photosensitivity and UV absorption of GeO(2)-SiO(2) solgel planar waveguides are presented. Photoinduced refractive-index changes in the samples are deduced from photosensitive grating writing experiments and are found to be of the order of those seen in some fiber experiments. A correlation is seen between the sample sensitivity and the strength of the absorption at 242 nm, providing insight into the possible mechanisms governing photosensitive processes in these materials.

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