Effect of the GeO₂ content on the radiation resistance of Er³⁺ -doped silica glasses and fibers

Abstract

In this work, Er/Al/Ge co-doped silica glasses with different GeO2 content (0–3 mol%), as well as Ge/Al co-doped silica glasses, are prepared by combining the sol–gel and high-temperature sintering methods. Further, the effects of the GeO2 content on the absorptions and emissions properties, and lifetimes of the glasses before and after 1KGy γ-ray irradiation are compared. The Er/Al/Ge co-doped silica fibers are prepared from a preform produced via modified chemical vapor deposition (MCVD) combined with nano sol-doping. The effects of Ge co-doping on the optical loss and amplifier gain of the Er-doped silica fibers (EDFs) before and after irradiation are also investigated. The related mechanism and species of the γ-ray radiation-induced color centers are revealed via radiation-induced-absorption (RIA) and continuous wave electron paramagnetic resonance (CW-EPR) spectroscopies. The results revealed that co-doping with GeO2 considerably improves the radiation resistance of the glass and exerts a slight effect on the spectral properties of the Er/Al/Ge co-doped silica glasses before irradiation. The RIA and CW-EPR spectra revealed that the aluminum–oxygen hole center (AlOHC) defects reduce with increasing GeO2 content because the intermediaries, the Ge-related oxygen-deficient centers (GeODC(I) and GeODC(II)), exhibit stronger abilities to trap the holes compared with the [AlO4/2]− group. This reduces the RIA level in the visible and near-infrared regions of the Er/Al/Ge co-doped silica glass. The irradiation experiment on the fiber further confirmed that the radiation resistance of EDFs can be considerably improved by Ge co-doping.

Influence of GeO2 Content on the Spectral and Radiation-Resistant Properties of Yb/Al/Ge Co-Doped Silica Fiber Core Glasses

“…Previous studies have shown that in Yb/Al co-doped silica glasses, Yb 3+ ions are coordinated in [AlO 4/2 ] − tetrahedra, and the following reactions occur during the irradiation process [ 21 , 25 ]: …”

“…However, it reduces the absorption and emission cross-sections of Yb 3+ ions, and the radiation resistance of the Yb/Al/P co-doped fiber is relatively weak [ 21 , 22 ]. It has been confirmed that Ge co-doping can reduce the radiation-induced absorption (RIA) caused by Al- and/or P-related defects during irradiation [ 23 , 24 ] and improve the radiation resistance of Er/Al/Ge co-doped glasses and fibers without negatively affecting the spectral properties of Er 3+ ions [ 25 ]. However, the effects of Ge co-doping on the spectral and radiation-resistant properties of Yb-doped silica glasses have not yet been reported.…”

Radiation-Resistant Er-Doped Fiber Based on Ge-Ce Co-Doping

“…In addition, recent studies have shown Ge-doping has a positive impact on radiation hardening in rare-earth-doped fibers [18]- [21]. It has been demonstrated that the introduction of Ge into the rare-earth doped fiber could induce the competition of hole-trapping or electron-trapping between the precursors of Al or P and Ge [19]. To cope with the harsher radiation environment for space missions, we use a Ge-Ce co-doping strategy in EDFs to enhance the radiation resistance.…”

Radiation‐induced darkening and its suppression methods in Yb3+‐doped silica fiber core glasses

“…researchers have proposed a variety of methods, such as photo-or thermal-bleaching, loading of hydrogen (H 2 ) or deuterium (D 2 ), 4,5 pre-irradiation, 6 and co-doping with other ions. 7,8 The RD effect in active fibers is the result of color center formation. [9][10][11][12][13] However, it is difficult to study the nature, precursor, and formation mechanism of color centers using optical fiber samples as the main research object.…”

“…Radiation‐induced darkening (RD) can lead to an increase in optical loss, a drastic decrease in the slope efficiency of the YDF laser, and no laser output in severe cases 3 . To suppress and mitigate the RD effect, researchers have proposed a variety of methods, such as photo‐ or thermal‐bleaching, loading of hydrogen (H 2 ) or deuterium (D 2 ), 4,5 pre‐irradiation, 6 and co‐doping with other ions 7,8 …”