• Infrared and Laser Engineering
  • Vol. 52, Issue 6, 20230242 (2023)
Xiaolin Wang1,2, Peng Wang1,2, Hanshuo Wu1,2, Yun Ye1..., Lingfa Zeng1, Baolai Yang1,2, Xiaoming Xi1,2, Hanwei Zhang1,2, Chen Shi1,2, Fengjie Xi1,2, Zefeng Wang1,2,*, Kai Han1,2, Pu Zhou1,*, Xiaojun Xu1,2 and Jinbao Chen1,2|Show fewer author(s)
Author Affiliations
  • 1College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
  • 2Nanhu Laser Laboratory, National University of Defense Technology, Changsha 410073, China
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    DOI: 10.3788/IRLA20230242 Cite this Article
    Xiaolin Wang, Peng Wang, Hanshuo Wu, Yun Ye, Lingfa Zeng, Baolai Yang, Xiaoming Xi, Hanwei Zhang, Chen Shi, Fengjie Xi, Zefeng Wang, Kai Han, Pu Zhou, Xiaojun Xu, Jinbao Chen. Design, simulation and implementation of direct LD pumped high-brightness fiber laser (invited)[J]. Infrared and Laser Engineering, 2023, 52(6): 20230242 Copy Citation Text show less
    SRS and TMI have conflicting requirements for fiber laser design
    Fig. 1. SRS and TMI have conflicting requirements for fiber laser design
    Structure of fiber with variable core diameter and its bending diagram for use in fiber lasers
    Fig. 2. Structure of fiber with variable core diameter and its bending diagram for use in fiber lasers
    Traditional laser pumping wavelength and new pumping waveband for optimized TMI threshold
    Fig. 3. Traditional laser pumping wavelength and new pumping waveband for optimized TMI threshold
    Power distribution and normalized B-integral in fiber amplifier under different pump configuration. (a) Power distribution in the amplifier; (b) Normalized B-integral
    Fig. 4. Power distribution and normalized B-integral in fiber amplifier under different pump configuration. (a) Power distribution in the amplifier; (b) Normalized B-integral
    Simulation of TMI thresholds in co-pump and counter pump configuration with a pump wavelength of 976 nm
    Fig. 5. Simulation of TMI thresholds in co-pump and counter pump configuration with a pump wavelength of 976 nm
    Simulation results of TMI threshold at different pump wavelengths in co-pump configuration of 30/400 μm amplifiers
    Fig. 6. Simulation results of TMI threshold at different pump wavelengths in co-pump configuration of 30/400 μm amplifiers
    TMI threshold and output Raman power of different fiber amplifiers
    Fig. 7. TMI threshold and output Raman power of different fiber amplifiers
    SeeFiberLaser simulation model of continuous fiber oscillator
    Fig. 8. SeeFiberLaser simulation model of continuous fiber oscillator
    Output spectrum of 1080 nm fiber oscillator with different ytterbium-doped fiber lengths. (a) Output spectrum when the ytterbium fiber is 10 m; (b) Output spectrum when the ytterbium fiber is 20 m
    Fig. 9. Output spectrum of 1080 nm fiber oscillator with different ytterbium-doped fiber lengths. (a) Output spectrum when the ytterbium fiber is 10 m; (b) Output spectrum when the ytterbium fiber is 20 m
    Fiber laser output spectrum at different central wavelengths. (a) Output spectrum when the central wavelength of the FBG is 1050 nm; (b) Output spectrum when the central wavelength of the FBG is 1080 nm
    Fig. 10. Fiber laser output spectrum at different central wavelengths. (a) Output spectrum when the central wavelength of the FBG is 1050 nm; (b) Output spectrum when the central wavelength of the FBG is 1080 nm
    Simulation results of output spectrum of the fiber laser oscillator employing output coupling fiber Bragg grating (OCFBG) with different reflectivities. (a) The reflectivity is 5%; (b) The reflectivity is 15%
    Fig. 11. Simulation results of output spectrum of the fiber laser oscillator employing output coupling fiber Bragg grating (OCFBG) with different reflectivities. (a) The reflectivity is 5%; (b) The reflectivity is 15%
    Output spectrum and resonator power distribution of different fiber lengths at 975 nm and 915 nm pumping. (a) Output spectrum when 975 nm pumped 15 m YDF; (b) Cavity power distribution when 975 nm pumped 15 m YDF; (c) Output spectrum when 915 nm pumped 30 m YDF; (d) Cavity power distribution when 915 nm pumped 30 m YDF
    Fig. 12. Output spectrum and resonator power distribution of different fiber lengths at 975 nm and 915 nm pumping. (a) Output spectrum when 975 nm pumped 15 m YDF; (b) Cavity power distribution when 975 nm pumped 15 m YDF; (c) Output spectrum when 915 nm pumped 30 m YDF; (d) Cavity power distribution when 915 nm pumped 30 m YDF
    V values corresponding to different core diameters and NAs
    Fig. 13. V values corresponding to different core diameters and NAs
    Multi-parameter optimization iteration and simulation results. (a) Various parameters that need to be iterated; (b) Simulation results under different simulation parameters
    Fig. 14. Multi-parameter optimization iteration and simulation results. (a) Various parameters that need to be iterated; (b) Simulation results under different simulation parameters
    Experimental setup of bi-direction pumped high power fiber laser
    Fig. 15. Experimental setup of bi-direction pumped high power fiber laser
    Comparision of the TMI and beam quality of the fiber amplifier employing spindle-shaped ytterbium-doped fiber and uniform ytterbium-doped fiber before and after pumping. TMI of the fiber amplifier employing (a) spindle-shaped ytterbium-doped fiber and (b) uniform ytterbium-doped fiber; (c) beam quality comparision of the fiber amplifier employing spindle-shaped and uniform ytterbium-doped fiber
    Fig. 16. Comparision of the TMI and beam quality of the fiber amplifier employing spindle-shaped ytterbium-doped fiber and uniform ytterbium-doped fiber before and after pumping. TMI of the fiber amplifier employing (a) spindle-shaped ytterbium-doped fiber and (b) uniform ytterbium-doped fiber; (c) beam quality comparision of the fiber amplifier employing spindle-shaped and uniform ytterbium-doped fiber
    Comparison of experimental results between SPF and 25/400 µm CCAF under the same conditions. (a) Beam quality of the output laser with CCAF; (b) Beam quality of the output laser with SPF; (c) Comparison of the spectra of the two fibers at the same output power
    Fig. 17. Comparison of experimental results between SPF and 25/400 µm CCAF under the same conditions. (a) Beam quality of the output laser with CCAF; (b) Beam quality of the output laser with SPF; (c) Comparison of the spectra of the two fibers at the same output power
    Experimental setup of 981 nm LD pumped 6 kW level oscillating-amplifying integrated fiber laser
    Fig. 18. Experimental setup of 981 nm LD pumped 6 kW level oscillating-amplifying integrated fiber laser
    Experimental results of the oscillating-amplifying integrated fiber laser. (a) Power efficiency characteristics; (b) Spectra in different power; (c) Beam quality
    Fig. 19. Experimental results of the oscillating-amplifying integrated fiber laser. (a) Power efficiency characteristics; (b) Spectra in different power; (c) Beam quality
    Experimental setup of 981 nm LD pumped 7 kW fiber laser with good beam quality
    Fig. 20. Experimental setup of 981 nm LD pumped 7 kW fiber laser with good beam quality
    Experiment results of the 7 kW fiber amplifier based on counter-pump with pump wavelength of 981 nm. (a) Power efficiency; (b) Spectra in different power; (c) Beam quality
    Fig. 21. Experiment results of the 7 kW fiber amplifier based on counter-pump with pump wavelength of 981 nm. (a) Power efficiency; (b) Spectra in different power; (c) Beam quality
    Experiment results of the high power fiber amplifier employing 27/600 μm fiber. (a) Power efficiency; (b) Spectra in different power; (c) Beam quality
    Fig. 22. Experiment results of the high power fiber amplifier employing 27/600 μm fiber. (a) Power efficiency; (b) Spectra in different power; (c) Beam quality
    Integrated multifunctional passive devices for replacing traditional splicing-based multiple passive devices. (a) Fusion splicing of four independent passive devices; (b) Four passive devices integrated on one single passive fiber without fusion points
    Fig. 23. Integrated multifunctional passive devices for replacing traditional splicing-based multiple passive devices. (a) Fusion splicing of four independent passive devices; (b) Four passive devices integrated on one single passive fiber without fusion points
    Illustration of ytterbium-doped and energy-transfer integrated fiber
    Fig. 24. Illustration of ytterbium-doped and energy-transfer integrated fiber
    Fabrication of functional passive devices on the passive fiber of ytterbium-doped and energy-transfer integrated fiber
    Fig. 25. Fabrication of functional passive devices on the passive fiber of ytterbium-doped and energy-transfer integrated fiber
    Gain-resonator integrated design. (a) Gain-resonator integrated design with FBGs directly written into the gain fiber; (b) Gain-resonator integrated design with FBGs written into the passive fiber of the ytterbium-doped and energy transfer integrated fiber
    Fig. 26. Gain-resonator integrated design. (a) Gain-resonator integrated design with FBGs directly written into the gain fiber; (b) Gain-resonator integrated design with FBGs written into the passive fiber of the ytterbium-doped and energy transfer integrated fiber
    Fiber laser directly pumped by high power LD without combiner
    Fig. 27. Fiber laser directly pumped by high power LD without combiner
    Illustration of high power fiber laser based on ytterbium-doped and energy transfer integrated fiber and integrated multifunctional passive devices
    Fig. 28. Illustration of high power fiber laser based on ytterbium-doped and energy transfer integrated fiber and integrated multifunctional passive devices
    YearCompany/InstituteConfigurationPump schemePower/kWBeam qualityBrightnessReference
    2009IPG Photonics,USAAmplifierTandem pump10M2~1.3 ~5.073×1015[26]
    2016NUDT, ChinaAmplifierTandem pump10--[27]
    2021Tsinghua, ChinaAmplifierTandem pump9.01--[28]
    2021CAEP & Tsinghua, ChinaAmplifierTandem pump20.01--[23]
    2021CAEP, ChinaAmplifierTandem pump20.88βfl~2.96 ~2.043×1015[21]
    2022CAEP, ChinaAmplifierTandem pump21.39βfl~3.86 ~1.231×1015[20]
    2022NUDT, ChinaAmplifierTandem pump20.22M2~3.3 ~1.592×1015[29]
    2017TJ Univ., ChinaAmplifierLD pump5.01<1.8~1.326×1015[30]
    2018CAEP, ChinaAmplifierLD pump10.6βfl~3.86 ~6.099×1014[31]
    2019SIOM, ChinaAmplifierLD pump10--[22]
    2020DK laser, ChinaAmplifierLD pump6M2~2.2 ~1.063×1015[32]
    2021NUDT, ChinaAmplifierLD pump6M2<1.3 >3.044×1015[16]
    2021NUDT, ChinaAmplifierLD pump8M2~2.5 ~1.097×1015[33]
    2022NUDT, ChinaAmplifierLD pump13M2~2.85 ~1.372×1015[34]
    2021Maxphotonics, ChinaAmplifierLD pump12BBP~1.2 mm·mrad8.443×1014[35]
    2021Raycus laser, ChinaAmplifierLD pump12BBP~3.6 mm·mrad9.382×1013[36]
    2022Raycus laser, ChinaAmplifierLD pump22.07M2 ~9.68 ~2.019×1014[24]
    2022NUDT, ChinaAmplifierLD pump20.27M2 ~7@15 kW ~2.625×1014[25]
    2014IPG PhotonicsOscillatorLD pump10M2<1.1 >7.085×1015[37]
    2018NUDT, ChinaOscillatorLD pump5M2~2.2,1.4 ~2.187×1015[38-39]
    2018Universität Jena, GermanyOscillatorLD pump4.8M2~1.3 ~2.435×1015[40-41]
    2019Lumentum, USAOscillatorLD pump4.2BBP~1.5 mm·mrad1.891×1014[42]
    2019GW laser, ChinaOscillatorLD pump4Single mode-[43]
    2019Reci laser, ChinaOscillatorLD pump4Single mode-[44]
    2019FeiBo laser, ChinaOscillatorLD pump4Ring laser-[45]
    2020DK laser, ChinaOscillatorLD pump5M2~2.4 ~7.442×1014[46]
    2020Fujikura, JapanOscillatorLD pump8M2~1.5 ~3.048×1015[10]
    2020NUDT, ChinaOscillatorLD pump7M2~2.4 ~1.042×1015[47]
    2022NUDT, ChinaOscillatorLD pump7.92M2~2.8 ~8.661×1014[48]
    2023Reci Laser, ChinaOscillatorLD pump6--[49]
    Table 1. Development of high efficiency fiber laser in recent years
    ParametersPhysical effects
    PowerTime domainBeam qualitySpectrumIn which laser
    ASEAll fiber laser
    SBSSingle-frequency and narrow linewidth fiber laser
    SRSAll fiber laser
    SPMAll fiber laser
    XPMNone single- frequency laser
    FWMNone single- frequency laser
    TMIAll fiber laser
    Table 2. Influence of physical effects on laser output characteristic parameters in fiber laser
    FiberCore diameter/µmCladding diameter/µm
    Fiber120-30-20400-600-400
    Fiber220400
    Fiber325500
    Fiber430600
    Table 3. Main parameters of fibers used in simulation
    ParameterValueParameterValue
    Spectrum shape of the pumpGaussianType of YDFUser-defined 20/400
    Central wavelength of the pump915-975 nmLength of YDF15-30 m
    3 dB linewidth of the pump3 nmCore diameter of YDF20 μm
    Forward pump power1000 WInner cladding diameter of YDF400 μm
    Backward pump power1000 WPump absorption coefficient1.26 dB/m@975 nm
    Reflection spectrum of HRFBGGaussianReflection spectrum of OCFBGGaussian
    Central wavelength of HRFBG1050-1090 nmCentral wavelength of OCFBG1050-1090 nm
    Reflectivity of the HRFBG99%Reflectivity of the OCFBG5%-30%
    Length of endcap’s pigtail fiber3 mLength of the rest pigtail fiber1 m
    Raman delayed response fraction0.18Raman noise1×10−12 W
    Raman gain coefficient1.22×10−14 s Vibration damping time3.2×10−14 s
    Nonlinear refractive index coefficient2.6×10−20 m2/W
    Table 4. Main parameters of fiber oscillator simulation
    Length of YDF/mSRS suppression ratio/dBResidual pump power/WOutput power/W
    1051.41601512.8
    1543.3461572.5
    2039.6161572.2
    Table 5. Fiber oscillator simulation results with different ytterbium-doped fiber lengths
    Central wavelength/nm ASE suppression ratio/dB SRS suppression ratio/dB Quantum efficiency Output power/W
    105032.5>32.50.92311480
    106043.5>43.50.91281558
    1070>4342.70.90261572.7
    1080>4544.30.89231572.4
    1090>4645.90.88211560
    Table 6. Simulation output parameters of fiber laser oscillators with different central wavelengths
    Reflectivity of the OCFBG SRS suppression ratio/dB Highest power within laser cavity/W Output power/W
    5%45.617631593.3
    10%43.318371572.5
    15%41.519241558.3
    30%27.822061487.1
    Table 7. Simulation results of output characteristics of the fiber laser oscillator employing output coupling fiber Bragg grating (OCFBG) with different reflectivities
    Pump wavelength/nm Length of YDF/m SRS suppression ratio/dB Residual pump power/W Output power/W
    9751543.3461572.5
    9153035801346.2
    91538.527.6451351.1
    9154526.7221332.9
    Table 8. Output parameters simulated for different pumping wavelengths and fiber lengths
    Wavelength/ μm Core diameter/ μm NA (maximum) NA (design)
    1.07250.0699<0.067
    1.07260.0672<0.065
    1.07270.0647<0.062
    1.07280.0624<0.061
    1.07290.0603<0.060
    1.07300.0583<0.056
    Table 9. Numerical apertures and core diameters of different optical fiber that supporting 6 modes
    ParameterValueParameterValue
    Core diameter25 μmHeat transfer coefficient2000
    Cladding diameter600 μmEnvironmental temperature25 ℃
    Pump absorption coefficient0.5-0.75 dB/m@976 nmCore diameter of the input signal fiber25 μm
    Pump wavelength976 nmCladding diameter of the input signal fiber600 μm
    Spectrum shape of the pumpGaussianLength of the input signal fiber1 m
    3 dB linewidth of the pump1 nmCore diameter of the output signal fiber50 μm
    Forward pump power2000 WLength of the output signal fiber1 m
    Length of the YDF25-35 mCore diameter of the endcap50 μm
    Backward pump power10000-12000 WLength of the endcap’s pigtail fiber2
    Seed power100 W
    Table 10. Simulation parameters of counter-pumped 25/600 μm fiber amplifier
    Fiber length/m Output power/W O-O efficiency SRS suppression ratio/dB
    258188.2080.88%41.10
    268223.4081.23%40.87
    278254.2081.54%40.09
    288280.8081.81%38.00
    298304.1082.04%37.55
    308324.0082.24%37.94
    318341.3082.41%37.76
    328356.5082.57%37.57
    338369.7082.70%36.44
    348381.4082.81%37.14
    358390.8082.91%34.39
    Table 11. Simulation results of a counter-pumped 25/600 μm fiber amplifier with different fiber lengths
    Pump absorption/ dB·m−1Output power/W O-O efficiency SRS suppression ratio/dB
    0.508141.7080.42%36.57
    0.558246.2081.46%36.29
    0.608324.0082.24%37.94
    0.658382.6082.83%37.61
    0.708427.0083.27%38.46
    Table 12. Simulation results of counter-pumped 25/600 μm fiber amplifier with different absorption coefficients
    Fiber length/m Pump power/W Output power/W O-E efficiency SRS suppression ratio/dB
    30100008324.082.24%37.94
    31100008341.382.41%37.76
    32100008356.582.57%37.57
    30110009146.182.24%34.46
    31110009165.3082.41%34.38
    32110009181.582.56%33.58
    30120009967.282.23%30.78
    31120009987.982.40%32.14
    321200010005.082.54%31.24
    Table 13. Simulation results of a counter-pumped 25/600 μm fiber amplifier with fiber length and different pumping powers
    Fiber core diameter/μm Output power/W O-O efficiency SRS suppression ratio/dB
    258323.382.23%31.05
    308323.782.24%34.59
    358323.682.24%35.83
    408323.782.24%35.90
    458323.982.24%36.80
    508324.082.24%37.73
    Table 14. Simulation results of counter-pumped 25/600 μm fiber amplifier with different passive fiber core diameters
    Fiber length/m Output power/W O-O efficiency SRS suppression ratio/dB
    28323.882.24%34.46
    38294.881.95%31.89
    48264.981.65%28.68
    58235.181.35%26.73
    Table 15. Simulation results of counter-pumped 25/600 μm fiber amplifier with different passive fiber lengths
    Pump wavelength/nm Pump direction Maximum power/W EfficiencyLimitation
    976Co-pump141784.5%TMI
    Counter-pump168885.3%TMI
    Bi-pump320385.3%TMI
    981Co-pump267084.3%SRS
    Counter-pump378486.8%TMI
    Bi-pump503084.2%SRS
    969Counter-pump407379.2%Pump power
    Table 16. Output characters of the fiber amplifiers with different pump wavelengths in experiment
    Xiaolin Wang, Peng Wang, Hanshuo Wu, Yun Ye, Lingfa Zeng, Baolai Yang, Xiaoming Xi, Hanwei Zhang, Chen Shi, Fengjie Xi, Zefeng Wang, Kai Han, Pu Zhou, Xiaojun Xu, Jinbao Chen. Design, simulation and implementation of direct LD pumped high-brightness fiber laser (invited)[J]. Infrared and Laser Engineering, 2023, 52(6): 20230242
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