Photosensitivity and grating writing in hydrogen loaded germanosilicate core optical fibers at 325 and 351 nm

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Abstract
A refractive indexgrating has been side written in the core of a hydrogen loaded germanosilicate optical fiber using a phase mask and 351 nm light from an Ar ion laser, the longest wavelength yet reported, to the best of our knowledge, for a grating of this type. The grating strength was ∼1.25 dB, indicating an index change of ∼2×10 −4 . The fiber was sensitized by low temperature hydrogen loading followed by a brief exposure to a CO 2 laser, resulting in the formation of high levels of germanium–oxygen deficiency centers. Fluorescence changes and UV transmission changes in hydrogen loaded germanosilicate glasses exposed to 325 nm and combined 351/364 nm radiation are also reported.