She, Shengfei; Liu, Bo; Chang, Chang; Xu, Yantao; Xiao, Xusheng; Cui, Xiaoxia; Li, Zhe; Zheng, Jinkun; Gao, Song; Zhang, Yan; Li, Yizhao; Zhou, Zhenyu; Mei, Lin; Hou, Chaoqi; Guo, Haitao

Further power scaling and stable laser performance were demonstrated in the Yb/Ce codoped aluminosilicate fiber fabricated through low-temperature chelate gas phase deposition technique. The molar ratio of Ce/Yb was designed and optimized to be 0.58 for low background loss, effective photodarkening suppression, and no additional thermal load. The background loss of this active fiber was 4.7 dB/km and its photodarkening loss at equilibrium was as low as 3.9 dB/m at 633 nm. Benefiting from low-temperature deposition technique, the fiber showed uniform core composition devoid of clustering and central 'dip' of refractive index profile and 0.19 mol% Yb2O3 was homogeneously dissolved into the fiber core plus with 0.41 mol% Al2O3, 0.11 mol% Ce2O3, and 0.32 mol% SiF4. Based on a master oscillator power amplifier laser setup, 5.04 kW laser output at 1079.80 nm was achieved with a slope efficiency of 81.1%. Stabilized at 5kW-level laser for over 60 minutes, the output power presented almost no power degradation, directly confirming a noticeable photodarkening mitigation.

The result was published on JOURNAL OF LIGHTWAVE TECHNOLOGY.  DOI: 10.1109/JLT.2020.3019740