The photosensitivity and its microstructural origin of Ge-doped silica fiber: Effect of H2 content

Abstract

Hydrogen (H₂) loading has been widely used to enhance the photosensitivity of germanium-doped fibers (GDF). However, the photosensitivity enhancement mechanism via H₂-loading remains unclear. In this work, GDF was prepared using modified chemical vapor deposition (MCVD) method. H₂-loading treatment is carried out on Ge-doped silica glass and fiber using high-pressure autoclave. A 248 nm KrF excimer laser was used to expose Ge-doped silica glass and fiber with or without H₂ loading. The influence of H₂ content on the photosensitivity of GDF was studied during the FBG inscription process, and the influence mechanism was revealed from the atomic level microscale. The evolution of H₂ content-dependent color centers caused by 248 nm laser irradiation and their characteristics in GDF core glasses was identified through photoluminescence (PL), radiation induced absorption (RIA), electron paramagnetic resonance (EPR) and other methods. The results showed that the Ge-ODCs content in the Ge-doped silica with H₂-loading decreased significantly after 248 nm laser irradiation, producing much more Ge(1), Ge-E ', H(II) color centers than the glass without H₂, but no Ge(2) was generated. The generation of Ge-E' was significantly enhanced in the presence of H(II). This work visually demonstrated the effect of H₂ loading on the enhancement of photosensitivity and further revealed H₂ significantly accelerated the rate of color center conversion.