• High Power Laser Science and Engineering
  • Vol. 10, Issue 6, 06000e44 (2022)
Hanshuo Wu, Haobo Li, Yi An, Ruixian Li, Xiao Chen, Hu Xiao*, Liangjin Huang, Huan Yang, Zhiping Yan, Jinyong Leng, Zhiyong Pan, and Pu Zhou
Author Affiliations
  • College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China
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    DOI: 10.1017/hpl.2022.31 Cite this Article Set citation alerts
    Hanshuo Wu, Haobo Li, Yi An, Ruixian Li, Xiao Chen, Hu Xiao, Liangjin Huang, Huan Yang, Zhiping Yan, Jinyong Leng, Zhiyong Pan, Pu Zhou. Transverse mode instability mitigation in a high-power confined-doped fiber amplifier with good beam quality through seed laser control[J]. High Power Laser Science and Engineering, 2022, 10(6): 06000e44 Copy Citation Text show less
    (a) Refractive index profile of the fiber across the core region; (b) cross-section photograph of the confined-doped fiber.
    Fig. 1. (a) Refractive index profile of the fiber across the core region; (b) cross-section photograph of the confined-doped fiber.
    Experimental schematic of the confined-doped fiber amplifier (PSC, pump and signal combiner; YDF, ytterbium-doped fiber; CMS, cladding mode stripper).
    Fig. 2. Experimental schematic of the confined-doped fiber amplifier (PSC, pump and signal combiner; YDF, ytterbium-doped fiber; CMS, cladding mode stripper).
    (a) The output power and optical-to-optical efficiency as a function of the pump power; (b) the beam quality factor evolution as a function of the output power.
    Fig. 3. (a) The output power and optical-to-optical efficiency as a function of the pump power; (b) the beam quality factor evolution as a function of the output power.
    The TMI threshold and extracted power as a function of seed laser power.
    Fig. 4. The TMI threshold and extracted power as a function of seed laser power.
    The experimental schematic of the power controllable seed laser based on the bending loss mechanism.
    Fig. 5. The experimental schematic of the power controllable seed laser based on the bending loss mechanism.
    The experimental schematic of the S2 measurement (TFL, tunable fiber laser; FUT, fiber under test; MO, microscope objective; CCD, charge-coupled device).
    Fig. 6. The experimental schematic of the S2 measurement (TFL, tunable fiber laser; FUT, fiber under test; MO, microscope objective; CCD, charge-coupled device).
    S2 measurement results when the bending diameter of the FUT is (a) 35 cm, (b) 20 cm, (c) 15 cm and (d) 8 cm.
    Fig. 7. S2 measurement results when the bending diameter of the FUT is (a) 35 cm, (b) 20 cm, (c) 15 cm and (d) 8 cm.
    Extracted power at different seed laser powers.
    Fig. 8. Extracted power at different seed laser powers.
    (a) TMI threshold and the power of the fundamental mode upon the onset of TMI and (b) the mode purity of the output laser as a function of the seed laser mode purity (simulation results).
    Fig. 9. (a) TMI threshold and the power of the fundamental mode upon the onset of TMI and (b) the mode purity of the output laser as a function of the seed laser mode purity (simulation results).
    The pump gain distribution of HOM-A along the fiber when the seed mode purities are 0.6 and 1.
    Fig. 10. The pump gain distribution of HOM-A along the fiber when the seed mode purities are 0.6 and 1.
    (a) Output power as a function of the pump power; (b) output spectra at different output powers.
    Fig. 11. (a) Output power as a function of the pump power; (b) output spectra at different output powers.
    The beam quality factor evolution as a function of the output power.
    Fig. 12. The beam quality factor evolution as a function of the output power.
    Bending stateABCDN
    Bending diameter/m~0.15~0.09~0.08~0.06No bending
    Bending length/m~1.0~1.0~0.75~0.5
    Seed power/W1401109070180
    Table 1. Bending diameter/length and the seed laser power at different bending states.
    ParameterValueParameterValue
    rcore20 μmrclad125 μm
    λp1018 nmλs1080 nm
    ${\sigma}_{\mathrm{ap}}$ 9.44 × 10–26 m2 ${\sigma}_{\mathrm{ep}}$ 7.30 × 10–25 m2
    ${\sigma}_{\mathrm{as}}$ 2.29 × 10–27 m2 ${\sigma}_{\mathrm{es}}$ 2.82 × 10–25 m2
    τ840 μsn4.94 × 1025 m-3
    L36 m $\rho {C}_0$ $1.55\times {10}^6$ J/(m3·K)
    ${k}_\mathrm{T}$ $1.2\times {10}^{-5}$ $\kappa$ 1.38 W/K
    Table 2. The main parameters of the fiber amplifier.
    Hanshuo Wu, Haobo Li, Yi An, Ruixian Li, Xiao Chen, Hu Xiao, Liangjin Huang, Huan Yang, Zhiping Yan, Jinyong Leng, Zhiyong Pan, Pu Zhou. Transverse mode instability mitigation in a high-power confined-doped fiber amplifier with good beam quality through seed laser control[J]. High Power Laser Science and Engineering, 2022, 10(6): 06000e44
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