High Power Laser Science and Engineering, Volume. 12, Issue 4, 04000e40(2024)
A 301 W narrow-linewidth in-band pumped Er:Yb co-doped fiber amplifier at 1585 nm and related modeling for dynamics study and optimization
Figures & Tables(11)
Fig. 1. Configuration of the high-power Er-Yb co-doped fiber laser system. SM-EYDF and LMA-EYDF represent 10/125 μm and 25/300 μm EYDF, respectively. CL, collimating lens; WM, wedge mirror; PM, power meter; RM, reflective mirror; AP, attenuation plate; HR-FBG, high-reflectivity fiber Bragg grating; OC-FBG, output coupler fiber Bragg grating; LD, laser diode; PSC, pump signal combiner; CLS, cladding light stripper; FPF, Fabry–Pérot filter; ISO, isolator; MFA, mode field adapter; PC, pump combiner.
Fig. 2. Experimental results of the in-band pumped EYDF amplifier. (a) Signal power versus pump power. (b) Corresponding slope efficiency. The slope efficiency 
is defined as 
, the proportion of the power that will transfer from the injected pump to the signal laser. (c) Spectrum changes with pump power at a large wavelength span. (d) Spectral evolution at a small wavelength span. (e) 3 dB bandwidth of laser versus signal power. (f) Residual pump power and pump absorption versus pump power.
Fig. 3. Beam quality of the EYDF amplifier. (a) Beam quality versus output power. At the output power of 301 W, (b) the beam profile at the waist position and (c) the 
value are measured.
Fig. 4. Temporal characteristics of the EYDF amplifier at different output powers. (a)–(c) The temporal signal, its probability density function (PDF) of intensity and its Fourier-transform spectrum at the output power of 9 W, respectively. (d)–(f) The results at the power of 301 W, where 
is the average intensity of the temporal signal.
Fig. 5. Simplified erbium energy levels and dynamic process of ion transitions for the in-band pumped EYDF amplifier.
Fig. 6. Simulation results of the in-band pumped EYDF amplifier. (a) Output signal power, (b) slope efficiency and (c) pump absorption versus pump power in the simulation and experiment. At the pump power of 2300 W, (d) power distribution of each spatial mode along the EYDF, (e) output spectrum and (f) spectral evolution in the fiber. M1, M2, M3, M4, M5 represent LP01, LP11a, LP11b, LP21a, LP21b modes, respectively.
Fig. 7. Characteristics of the output laser for different pump powers in simulation. (a) Variation of the centroid of the gain spectrum (gain redshift) in the gain fiber with pump power. (b) Beam quality of the output laser versus pump power. The inset exhibits the beam profile of the output laser at the pump power of 2300 W. (c) Spectral evolution at different pump powers. (d) The output laser’s 3, 10 and 20 dB bandwidths under different pump powers in our simulation and experiment.
Fig. 8. Effect of PIQ, ESA, Er ion concentration and seed wavelength on the EYDF amplifier. (a) Effect of PIQ on output signal power and (b) pump absorption of the EYDF. (c) Effect of ESA on output signal power and (d) pump absorption. (e), (f) Results about the impact of Er ion concentrations. (g) Impact of the seed wavelength on signal power and output spectrum. The inset shows output spectra for different-wavelength seeds.
Fig. 9. Distributions of erbium ions among energy levels on the cross-section (
.
Fig. 10. Simulated results of the optimized in-band pumped EYDF amplifier. (a) Signal power distribution across all spatial modes in the EYDF. The inset shows the pump power distribution in the EYDF. (b) Output signal spectrum at the pump power of 2300 W. The inset exhibits the beam profile of the output laser. (c) Signal power distributions along the fiber for two EYDFs with different core-to-cladding ratios at the pump power of 2300 W.
Table 1. Some parameters used in the simulation.
View tableView in ArticleTable 1. Some parameters used in the simulation.
Sym./unit Physical meaning Value ${\mathrm{N}}_{\mathrm{er}}/{\mathrm{m}}^{-3}$ Er ion concentration $2.3\times {10}^{25{\phantom{A^{A}}}}$ $f$ The proportion of the number of paired ions 0.16 ${\sigma}_{\mathrm{ap}}/{\mathrm{m}}^2$ Absorption cross–section at the pump wavelength $4.74\times {10}^{-25}$ ${\sigma}_{\mathrm{ep}}/{\mathrm{m}}^2$ Emission cross–section at the pump wavelength $4.75\times {10}^{-25}$ ${\sigma}_{12,j}\left({\sigma}_{21,j}\right)/{\mathrm{m}}^2$ Absorption (emission) cross–section at signal wavelength ${\lambda}_{j}$ Ref. [ 20 ]${\sigma}_{\mathrm{ESA},\mathrm{p}}/{\mathrm{m}}^2$ Absorption cross–section for ESA at 1535 nm $8.06\times {10}^{-26}$ ${\sigma}_{\mathrm{ESA},\mathrm{s}}/{\mathrm{m}}^2$ Absorption cross–section for ESA at 1585 nm $3.07\times {10}^{-25}$ ${\tau}_{21}/\mathrm{s}$ Relaxation time for level 2 ( ${{}^4I}_{13/2}$ ${{}^4I}_{15/2}$ $7\times {10}^{-3}$ ${\tau}_{31}/\mathrm{s}$ Relaxation time for level 3 ( ${{}^4I}_{13/2}$ ${{}^4I}_{15/2}$ $7\times {10}^{-3}$ ${\tau}_{32}/\mathrm{s}$ Relaxation time for level 3 ( ${{}^4I}_{13/2}$ ${{}^4I}_{13/2}$ $1\times {10}^{-12}$ ${\tau}_{43}/\mathrm{s}$ Relaxation time for level 4 ( ${{}^4I}_{9/2}$ ${{}^4I}_{13/2}$ $5.2\times {10}^{-6}$ ${\tau}_{42}/\mathrm{s}$ Relaxation time for level 4 ( ${{}^4I}_{9/2}$ ${{}^4I}_{13/2}$ $5.2\times {10}^{-6}$
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Guohao Fu, Guanzhong Li, Weilong Yu, Pei Li, Dan Li, Qirong Xiao, Mali Gong, Ping Yan. A 301 W narrow-linewidth in-band pumped Er:Yb co-doped fiber amplifier at 1585 nm and related modeling for dynamics study and optimization[J]. High Power Laser Science and Engineering, 2024, 12(4): 04000e40
Paper Information
Category: Research Articles
Received: Dec. 9, 2023
Accepted: Mar. 25, 2024
Published Online: Sep. 20, 2024
The Author Email: Ping Yan (pyan@mail.tsinghua.edu.cn)
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