In recent years, kinds of methods have been proposed to mitigate the photo-darkening effect in ytterbium (Yb) -doped fiber lasers and amplifiers, including photo-bleaching, co-doping with ions, thermal-bleaching, H2/O2-loading, et al. Al, Ce, P, et al. are usually used in co-doping menthod. However, the addition of phosphorus and cerium will raise the fiber numerical aperture (NA), induce fiber background loss, and further reduce the slope efficiency of fiber lasers. Besides, phosphorus dopant also decreases the absorption and emission cross section of Yb ions. Therefore, it’s important to find an effective way to mitigate the PD effect without any fiber laser properties deterioration.
Wuhan National Laboratory for Optoelectronics fiber laser technology group(FLTG) Professor Li Jinyan, Engineer Li Haiqing,andDoctor Zhao Nan firstly proposed to dope Na+ ions into the Yb/Al co-doped fiber. The results showed that, by doping Na+ ions into the fiber core, the PD induced excess loss at 633, 702, 810, and 1041nm was reduced to 115.54dB/m, 86.87dB/m, 25.51dB/m, and 2.92dB/m, respectively. Compared to the Yb/Al co-doped fiber without Na+ ions, more than 30% PD loss was decreased. The laser efficiency of Yb/Al/Na co-doped fiber was measured to be 76.1% and the background loss was 51 dB/km, which were almost the same as Yb/Al co-doped fiber. The results demonstrate that the addition of Na+ ions is a convenient method to improve the PD resistance in Yb-doped fiber and keep fiber lasers operating with good performance.
On July 24, 2017, this work entitled with “Mitigation of photodarkening effect in Yb-doped fiber through Na+ ions doping” has been published in Optics Express (Vol. 25, Issue 19, (2017)) in the optical society of America (OSA). This work was financially supported by the National Key Research and Development Program of China (Grant No. 2016YFB0402201).
