Theoretical and Experimental Investigations of Beam‐Quality Variation Characteristics of High‐Power Thulium‐Doped Fiber Lasers

Sijie Wang; Xiaolong Chen; Hui Shen; Xiaochen Guo; Chuanfa Jia; Junxuan Zhang; Yunfeng Qi; Xisheng Ye

doi:10.3788/CJL241225

Chinese Journal of Lasers, Volume. 52, Issue 7, 0701001(2025)

Theoretical and Experimental Investigations of Beam‐Quality Variation Characteristics of High‐Power Thulium‐Doped Fiber Lasers

Sijie Wang^1,2,3, Xiaolong Chen^1,2,3, Hui Shen^1,2,3, Xiaochen Guo^1,3, Chuanfa Jia^1,3, Junxuan Zhang^2,3,4, Yunfeng Qi^1,2,3、*, and Xisheng Ye^1,2,3、**

Author Affiliations

¹Wang Zhijiang Laser Innovation Center, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

²College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China

³Aerospace Laser Technology and System Department, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

⁴Key Laboratory of Space Laser Communication and Detection Technology, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

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Figures & Tables(15)

Fig. 1. Illustration of beam quality prediction model^[12]

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Fig. 2. Schematic diagram of cross-section structure of double-cladding thulium-doped fiber

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Fig. 3. Laser performance under different total pump power conditions. (a) Output power; (b) temperature distribution in radial direction; (c) temperature distribution in longitudinal direction

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$Results under different total pump power conditions. (a) Thermally induced refractive index distribution of bending fiber after modification; (b) predicted M2$

Fig. 4. Results under different total pump power conditions. (a) Thermally induced refractive index distribution of bending fiber after modification; (b) predicted M²

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Fig. 5. Laser output performance under different pump ratios. (a) Output power; (b) temperature distribution in radial direction; (c) temperature distribution in longitudinal direction

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$Results under different pump ratios. (a) Thermally induced refractive index distribution of bending fiber after modification; (b) predicted M2$

Fig. 6. Results under different pump ratios. (a) Thermally induced refractive index distribution of bending fiber after modification; (b) predicted M²

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Fig. 7. Laser output performance under different active fiber absorption coefficients. (a) Output power; (b) temperature distribution in radial direction; (c) temperature distribution in longitudinal direction

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$Results under different active fiber absorption coefficients. (a) Thermally induced refractive index distribution of bending fiber after modification; (b) predicted M2$

Fig. 8. Results under different active fiber absorption coefficients. (a) Thermally induced refractive index distribution of bending fiber after modification; (b) predicted M²

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Fig. 9. Laser output performance under different seed laser power conditions. (a) Output power; (b) temperature distribution in radial direction; (c) temperature distribution in longitudinal direction

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$Results under different seed laser power conditions. (a) Thermally induced refractive index distribution of bending fiber after modification; (b) predicted M2$

Fig. 10. Results under different seed laser power conditions. (a) Thermally induced refractive index distribution of bending fiber after modification; (b) predicted M²

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Fig. 11. Beam quality research system with all-fiber MOPA structure^[18]

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Fig. 12. Measured M² under different conditions. (a) Total pump power; (b) R′; (c) seed power

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Fig. 13. Prediction deviations of M² under different conditions. (a) Input pump power; (b) R′; (c) seed power

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Fig. 14. Results under seed power of 15 W and pump ratio of 1∶1. (a) Output power of amplifier versus input pump power; (b) spectrum under amplifier output power of 513 W; (c) beam quality factor M²

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Table 1. Parameters used in simulation of laser output beam quality

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Table 1. Parameters used in simulation of laser output beam quality

Parameter	Value	Parameter	Value
Core radius， $a$	12.5 μm	Pump power， $P_{p u m p}$	100， 200， 300， 400， 1000 W
Cladding radius， $b$	200 μm	Seed power， $P_{s e e d}$	15， 20， 25， 30， 35 W
Coating radius， $c$	265 μm	Active fiber length， $L$	4.0， 5.6， 11.2 m
Pump wavelength， $λ_{p}$	793 nm	Fiber absorption coefficient， $α$	1.5 dB/m， 3.0 dB/m， 4.2 dB/m
Signal wavelength， $λ_{s}$	1940 nm	Emission cross-section at pump wavelength， $σ_{e p}$	0.5×10^-25 m^{-3 ［13］}
Fiber bending radius， $R$	47.5 mm	Absorption cross-section at pump wavelength， $σ_{e s}$	1.5×10^-25 m^{-3 ［13］}
Heat conductivity of core， $κ_{1}$	1.38 W/（m·K） ^［14］	Emission cross-section at lasing wavelength， $σ_{a p}$	10×10^-25 m^{-3 ［13］}
Heat conductivity of cladding， $κ_{2}$	1.38 W/（m·K） ^［14］	Absorption cross-section at lasing wavelength， $σ_{a s}$	0.1×10^-25 m^{-3 ［13］}
Heat conductivity of coating， $κ_{3}$	0.2 W/（m·K） ^［14］	Coolant temperature， $T_{c}$	12 ℃
Thermal optical coefficient， $β$	1.16×10^-5 K^{-1 ［14］}	Poisson ratio， $p_{e}$	0.17^［16］
Convective heat transfer coefficient， $h$	50 W·m^-2·K^-1［24］

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Sijie Wang, Xiaolong Chen, Hui Shen, Xiaochen Guo, Chuanfa Jia, Junxuan Zhang, Yunfeng Qi, Xisheng Ye. Theoretical and Experimental Investigations of Beam‐Quality Variation Characteristics of High‐Power Thulium‐Doped Fiber Lasers[J]. Chinese Journal of Lasers, 2025, 52(7): 0701001

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Paper Information

Category: laser devices and laser physics

Received: Sep. 23, 2024

Accepted: Dec. 3, 2024

Published Online: Apr. 16, 2025

The Author Email: Yunfeng Qi (dreamer_7@siom.ac.cn), Xisheng Ye (xsye@siom.com)

DOI:10.3788/CJL241225

CSTR:32183.14.CJL241225

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology