Photochemical reaction of hydrogen with germanosilicate glass initiated by 3.4 5.4-eV ultraviolet light.

By measuring the photosensitivity of Ge-doped silica fibers over the 3.4-5.4-eV spectral range and from T=95 K to T=375 K , we demonstrate that different physical mechanisms take place depending on whether H(2) is present. Without H(2) the principal photosensitivity pathway involves excitation of a germanium oxygen-deficient center to its triplet state. In H(2) -loaded fibers the UV light excites the regular Ge-O bond, which then reacts with H(2) to produce Si-OH or Ge-OH and a GeE(') center.