[1] Shi W, Fang Q, Zhu X S, et al. Fiber lasers and their applications[J]. Applied Optics, 53, 6554-6558(2014).

[2] Zheng Y, Yang Y, Wang J, Hu M, et al. 10.8 kW spectral beam combination of eight all-fiber super-fluorescent sources and their dispersion compensation[J]. Optics Express, 24, 12063-12071(2016).

[3] Liu Z, Ma P, Su R, Tao R, et al. High-power coherent beam polarization combination of fiber lasers: Progress and prospect[J]. Journal of the Optical Society of America B, 34, A7-A14(2017).

[4] Muller M, Klenke A, Steinkopff A, et al. 3.5 kW coherently combined ultrafast fiber laser[J]. Optics Letter, 43, 6037-6040(2018).

[5] Huang Y, Xiao Q, Li D, et al. 3 kW narrow linewidth high spectral density continuous wave fiber laser based on fiber Bragg grating[J]. Optics & Laser Technology, 133, 106538(2021).

[6] Lai W C, Ma P F, Xiao H, et al. High-power narrow-linewidth fiber laser technology[J]. High Power Laser and Particle Beams, 32, 7-28(2020).

[7] Wang Y, Sun Y, Peng W, et al. 3.25  kW all-fiberized and polarization-maintained Yb-doped amplifier with a 20  GHz linewidth and near-diffraction-limited beam quality[J]. Appl Optics, 60, 6331-6336(2021).

[8] [8] Agrawal G P. Nonlinear Fiber Optics[M]. New Yk: Academic Press, 2007.

[9] Cozens J R, Boucouvalas A C. Coaxial optical coupler[J]. Electronics Letters, 18, 138-140(1982).

[10] [10] Laperle P, Paré C, Zheng H, et al. Ybdoped LMA tripleclad fiber laser[C]Proc SPIE, Photonics Nth, 2006, 6343: 63430X.

[11] [11] Laperle P, Pare C, Zheng H, et al. YbDoped LMA tripleclad fiber f power amplifiers[C]Proceedings of SPIE, 2007, 6453: 645308.

[12] Leich M, Just F, Langner A, et al. Highly efficient Yb-doped silica fibers prepared by powder sinter technology[J]. Optics Letter, 36, 1557-1559(2011).

[13] Smith A V, Smith J J. Increasing mode instability thresholds of fiber amplifiers by gain saturation[J]. Optics Express, 21, 15168-15182(2013).

[14] Zhang L, Lou F G, Wang M, et al. Yb-Doped triple-clad fiber for nearly 10 kW level tandem-pumped output[J]. Chinese Journal of Lasers, 48, 1315001(2021).

[15] Yan P, Huang Y, Sun J, et al. 3.1 kW monolithic MOPA configuration fibre laser bidirectionally pumped by non-wavelength-stabilized laser diodes[J]. Laser Physics Letter, 14, 080001(2017).

[16] Huang Y, Yan P, Wang Z, et al. 2.19 kW narrow linewidth FBG-based MOPA configuration fiber laser[J]. Optics Express, 27, 3136(2019).

[17] [17] Liu S, Zhan H, Peng K, et al. kWlevel triplecladding laser fiber[C]Frontiers in OpticsLaser Science, 2018: JTu2A.24.

[18] Liu S, Zhan H, Peng K, et al. Yb-doped aluminophosphosilicate triple-clad laser fiber with high efficiency and excellent laser stability[J]. IEEE Photonics, 11, 1-10(2019).

[19] Chu Q, Shu Q, Liu Y, et al. 3 kW high OSNR 1030 nm single-mode monolithic fiber amplifier with a 180 pm linewidth[J]. Optics Letter, 45, 6502-6505(2020).

[20] Wang Y, Po H. Dynamic characteristics of double-clad fiber amplifiers for high-power pulse amplification[J]. J Lightwave Technol, 21, 2262(2003).

[21] Yan M, Wang Z, Meng L, et al. Heat suppression of the fiber coating on a cladding light stripper in high-power fiber laser[J]. Applied Optics, 57, 485-491(2018).

[22] [22] Feng Y, Wang X, Ke W, Sun Y, et al. Numerical analysis to fourwave mixing induced spectral broadening in high power fiber lasers[C]Proceedings of SPIE, 2015, 9255: 92550Q.

[23] Ke W W, Wang X J, Bao X F, et al. Thermally induced mode distortion and its limit to power scaling of fiber lasers[J]. Optics Express, 21, 14272-14281(2013).

[24] Wang Z, Yan M J, Yin L, et al. Stripping of cladding light at different angles: Theoretical and experimental studies[J]. Chinese Optics, 12, 1124-1130(2019).