We report a novel pretreatment method to improve the radiation resistance of Er-doped fiber (EDF). The processing object of this method is EDF preform, and the pretreatment processing involves three steps: deuterium loading, pre-irradiation, and thermal annealing. The effects of pretreatment conditions on the optical loss, gain performance, and radiation resistance of EDF were systematically studied. The relevant mechanisms were revealed using Fourier transform infrared (FTIR), radiation-induced absorption (RIA), and electron paramagnetic resonance (EPR) spectroscopies. The results show that the pretreatment can not only greatly reduce the hydroxyl content of the EDF core, but it can also effectively improve the radiation resistance of EDF. The online test results show that the gain of the commercial, pristine, and pretreated EDFs were reduced by 19.0, 4.2, and 1.3 dB, respectively, corresponding to a decrease of 68.1, 16.2, and 4.7% after 98 krad X-rays irradiation. The high vacuum experiments show that the pretreatment method can maintain long-term stable high radiation resistance. This work provides a reference for the development of high-performance radiation resistant EDFs for use in the lower, middle, and geosynchronous earth orbit.

In this study, a pretreatment method for improving the radiation resistance of Er-Yb co-doped silica fiber (EYDF) is proposed. EYDF is the object in this method and is processed by two steps, including deuterium loading and pre-irradiation. The effects of pretreatment conditions on the laser performance and radiation resistance of EYDF were systematically studied. An online irradiation experiment setup was utilized to evaluate the radiation resistance of EYDF. The results demonstrate that the pretreatment can significantly improve the radiation resistance of EYDF, with minimal impact on the laser output power and slope efficiency. Specifically, the radiation-induced gain variations in the pristine fiber and the pretreated fiber with a cumulative dose of 240 krad were 3.13 dB and 1.81 dB, respectively. Additionally, the high-vacuum experiments show that the proposed pretreatment method can maintain a long-term stable radiation resistance improvement in the fiber. This study provides a method to improve the radiation resistance of EYDF for space applications.

In this paper, we report the design, fabrication, and characterization of a passive silicate-glass-based all-solid anti-resonant fiber (AS-ARF) for ∼1 µm transmission suppression. Simulation results demonstrate that the AS-ARF achieves a first high higher order mode (HOM) suppression ratio of over 25 dB in a 26-63 µm core diameter at 1550 nm. Using the drilling and rod-in-tube technique, an AS-ARF was fabricated with a core diameter of 43 µm, a core NA of 0.023, and high-refractive-index capillaries (HRICs) thickness of 1.4 µm. Furthermore, a wide transmission window around 1.5 µm, and a high-loss resonant band ranging from 1 µm to 1.1 µm were measured, which agrees well with the simulation. By fusion spliced a 12 cm-long AS-ARF in the EYDF amplifier, amplified spontaneous emission (ASE) and parasitic oscillations of Yb³⁺ ions are effectively suppressed, and the loss at 1030 nm is 12.3 dB higher than that at 1550 nm. To the best of our knowledge, this is the first time that an AS-ARF can achieve ∼1 µm transmission suppression and single-mode propagation in the 1.5 µm band. The fiber structure option holds potential for further application in rare-earth-doped fiber amplifiers and lasers, including those doped with Nd, Yb, Er, Tm, and other rare-earth elements.

In this study, Yb/Al/Ge co-doped silica fiber core glasses with different GeO₂ contents (0–6.03 mol%) were prepared using the sol–gel method combined with high-temperature sintering. The absorption, fluorescence, radiation-induced absorption, continuous-wave electron paramagnetic resonance spectra, and fluorescence decay curves were recorded and analyzed systematically before and after X-ray irradiation. The effects of GeO₂ content on the valence variations of Yb³⁺/Yb²⁺ ions, spectral properties of Yb³⁺ ions, and radiation resistance of Yb/Al/Ge co-doped silica glasses were systematically studied. The results show that even if the GeO₂ content of the sample is relatively low (0.62 mol%), it can inhibit the generation of Yb²⁺ ions with slight improvement in the spectral properties of Yb³⁺ ions in the pristine samples and effectively improve its radiation resistance. Direct evidence confirms that the generation of trapped-electron centers (Yb²⁺/Si-E’/Al-E’) and trapped-hole centers (Al-OHC) was effectively inhibited by Ge co-doping. This study provides a theoretical reference for the development of high-performance, radiation-r esistant Yb-doped silica fibers.