3 kW 20/400 Yb-Doped Aluminophosphosilicate Fiber With High Stability

• Main Authors: Shuang Liu, Kun Peng, Huan Zhan, Li Ni, Xiaolong Wang, Yuying Wang, Yuwei Li, Juan Yu, Lei Jiang, Rihong Zhu, Jianjun Wang, Feng Jing, Aoxiang Lin
• Format: Article
• Language: English
• Published: IEEE 2018-01-01
• Series: IEEE Photonics Journal
• Subjects: Fiber design and fabrication; lasers; fiber; fiber optics amplifiers and oscillators.
• Online Access: https://ieeexplore.ieee.org/document/8423065/

By using the MCVD system and the all-gas-phase chelate precursor doping technique, we fabricated an Yb-doped aluminophosphosilicate fiber with 20 μm-core and 400 μm-clad in diameter, i.e., 20/400 Yb-APS fiber. The fiber core was doped with 1100 ppm Yb³⁺, 7200 ppm Al³⁺, and 8000 ppm P⁵⁺. With a molar ratio of Al/P close to 1:1, low refractive index difference and suitable numerical aperture was obtained for large-mode-area fiber design. Directly forward pumped by 976 nm laser diodes, 11-m-long 20/400 Yb-APS fiber presented 3.03 kW laser output at 1080 nm with a slope efficiency of 76.6% and beam quality M² of ~1.58. Up to this power level, no signs of instable beam profile, beam quality worsening, and laser power roll-over were obtained, indirectly justified no obvious mode instability in the whole laser setup. To directly characterize its power stability and photodarkening effect, the fiber laser was kept at ~2.1 kW for over 500 min with power degradation less than 1.1%. These results indicated that the all-gas-phase chelate precursor doping technique is highly competitive for Yb-APS fiber fabrication toward high-power laser, and the fabricated fiber is very suitable for 2 kW-level or above commercial fiber laser development.