Correlation of defect centers with a wavelength-dependent photosensitive response in germania-doped silica optical fibers

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 oxygen-deficient germania site creates hole traps, modeled as Ge E′ centers, which are detectable with electron spin reasonance spectroscopy.