Advanced Ce-free radiation-resistant Er/Yb fiber with high laser efficiency and mechanism analysis

Radiation-resistant Er/Yb co-doped fibers (EYDFs) hold significant promise for space applications, where maintaining high laser performance under irradiation is a critical requirement. The widely used Ce-doping approach provides strong radiation resistance, yet it also degrades the intrinsic laser performance of the fiber. Moreover, Ce increases the core refractive index, which limits the allowable Er/Yb concentrations. In this work, we fabricate a Ce-free radiation-resistant polarization-maintaining EYDF with enhanced laser characteristics. The removal of Ce allows higher Er/Yb concentrations and increases the absorption coefficient, allowing shorter fiber lengths to be used in practical systems and reducing radiation-induced degradation. Under identical operating conditions, the novel fiber achieves a laser efficiency of 46.4%, compared with 38.9% for the Ce-doped fiber, while exhibiting comparable radiation resistance under the same X-ray irradiation environment. We further analyze the mechanisms of its laser performance and radiation resistance through radiation-induced absorption (RIA) measurements, transmission electron microscopy (TEM), and fluorescence lifetime characterization.