Hydrogen-Related Anti-Radiation Effect and Its Suppression Mechanism in Er3+/Al3+/Ge4+ Co-Doped Silica Fibers

The antiradiation effect and evolution process of color center defects in hydrogen-treated Er ³⁺ /Al ³⁺ /Ge ⁴⁺ codoped fiber under radiation were studied. The radiation-induced absorption spectra and continuous wave electron paramagnetic resonance spectra of glass slice samples were tested to explain the mechanism of internal defect transformation. The hydrogen treatment reduces radiation-induced absorption and increases loss in the working band by the combination of the Ge-related short wavelength absorption edge effect and the absorption peak of hydrogen vibration. Thus, there is an optimal hydrogen concentration for decreasing the radiation-induced gain variation (RIGV) of optical fibers, and the fiber with 3 × 10 ¹⁹ cm ⁻³ hydrogen content had the lowest RIGV of approximately 0.038 dB/krad. The radiation-induced absorption and continuous wave electron paramagnetic property revealed that the hydrogen treatment suppresses Al-OHC and Ge dangling bands in optical fibers. Hydrogen also generates H(I), Si-E', and Ge-E' defects in the irradiation environment. This work helps to elucidate how hydrogen improves the radiation resistance of Er ³⁺ /Al ³⁺ /Ge ⁴⁺ codoped silica fibers.