[1] [1] Zervas M N, Codemard C A. High power fiber lasers: a review[J]. IEEE Journal of selected topics in Quantum Electronics, 2014, 20(5): 219-241.

[2] [2] Gao W, Fan W, Ju P, et al. Thermally-induced transverse mode instability: Hopf bifurcation in high-power fiber laser[J]. Results in Physics, 2022, 43: 106098.

[3] [3] Eidam T, Hanf S, Seise E, et al. Femtosecond fiber CPA system emitting 830 W average output power[J]. Optics letters, 2010, 35(2): 94-96.

[6] [6] Huang Z, Shu Q, Luo Y, et al. 3.5 kW narrow-linewidth monolithic fiber amplifier at 1064 nm by employing a confined doping fiber[J]. Journal of the Optical Society of America B, 2021, 38(10): 2945-2952.

[9] [9] Wang G, Song J, Chen Y, et al. Six kilowatt record all-fiberized and narrow-linewidth fiber amplifier with near-diffraction-limited beam quality[J]. High Power Laser Science and Engineering, 2022, 10: e22.

[10] [10] Du S, Fu G, Qi T, et al. 3.3 kW narrow linewidth FBG-based MOPA configuration fiber laser with near-diffraction-limited beam quality[J]. Optical Fiber Technology, 2022, 73: 103011.

[11] [11] Wu H, Song J, Ma P, et al. Bidirectional tandem-pumped high-brightness 6 kW level narrow - linewidth confined-doped fiber amplifier exploiting the side-coupled technique[J]. Optics Express, 2022, 30(12): 21338-21348.

[12] [12] Wan Y, Yang B, Xi X, et al. Comparison and optimization on transverse mode instability of fiber laser amplifier pumped by wavelength-stabilized and non-wavelength-stabilized 976 nm laser diode[J]. IEEE Photonics Journal, 2021, 14(1): 1-5.

[13] [13] Jauregui C, Otto H J, Breitkopf S, et al. Optimizing high-power Yb-doped fiber amplifier systems in the presence of transverse mode instabilities[J]. Optics Express, 2016, 24(8): 7879-7892.

[14] [14] Wang K, Mizuno Y, Su X, et al. Core diameter and numerical aperture dependences on the performance of fiberoptic multimode interference sensing[J]. Applied Physics Express, 2022, 16(1): 012003.

[15] [15] Otto H J, Modsching N, Jauregui C, et al. Impact of photo darkening on the mode instability threshold[J]. Optics Express, 2015, 23(12): 15265-15277.