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In a high-power fiber laser system, the reflected light generated when the laser hits the target may be recoupled to the laser and amplified by the laser, thereby damaging the laser system. This situation is particularly serious for a high-power laser system, such as spectral beam combining a high power fiber laser, which lacks effective light-return protection. In order to solve the above problems, it is necessary to integrate various physical effects in the whole system link, evaluate and analyze the influence of reflected light on the operating state of the system, so as to optimize the optical path layout and system structure in the beginning of the design of fiber laser to avoid unnecessary losses. Based on the atmospheric transmission theory, fiber rate equation and medium heat conduction equation model, the effect of reflected light on high-power fiber laser is analyzed. In this paper is conducted the numerical simulation of coupling efficiency of reflected light of high-power fiber laser. It is found that under certain atmospheric conditions, the reflected power is related to the transmission distance, the offset angle of optical axis, divergence angle, and the offset of center position of the beam, and will affect the output power, beam quality factor, thermal effect and the signal-to-noise ratio of the stimulated Raman scattering spectrum of the fiber laser. The coupling efficiency of reflected light has a maximum value at a certain transmission distance. For example, the reflected light power up to 140 W is obtained when the transmission distance is 1500 m, which will largely affect the laser system. The reflected power is affected by the offset angle of optical axis far less than by the transmission distance when transmission increases from 500 m to 2000 m. For example, a change of less than 0.1 W can be obtained when offset angle increases from 0.11° to 0.44°. It is also shown that as the divergence angle changes from 0 to 15'', the coupling power decays nearly exponentially with the divergence angle. The coupling efficiency is close to 1% near 12'', which is almost negligible. The output beam quality of the laser system is also affected by the beam quality of reflected light. Deterioration of the beam quality of reflected light will lead to the deterioration of the laser output beam quality. As the reflected light power enters the fiber laser system and increases, the forward output power will decrease and the backward signal power will increase, and the Raman power will increase rapidly near the fiber output end. When the reflected light is present, the thermal effects caused by selecting the gain fiber with different pump absorption coefficients are very important. The stimulated Raman scattering (SRS) rejection ratio decreases with the increase of pump absorption coefficient. For example, the SRS rejection ratio decreases by 5 dB when pump absorption coefficient increases from 1.5 dB/m to 4.5 dB/m, resulting in a decrease in the signal-to-noise ratio of the laser, which will reduce the reliability of the fiber laser system. In the design and test of spectral beam combining systems for high-power fiber lasers, the attention should be paid to the reflected light in the entire process, which includes the outer optical path and the internal optical path of the laser. The comprehensive constraints of multiple key indicators are analyzed, and the probability of system damage or reliability degradation due to reflected light is evaluated. The research results of this paper are of certain guiding significance in selecting suitable outer optical path layout and system parameters and also in optimizing the design of high energy fiber laser system. -
Keywords:
- fiber lasers /
- reflected light /
- atmospheric transmission /
- fiber coupling
[1] Koester C J, Snitzer E 1964 Appl. Opt. 3 1182
Google Scholar
[2] Shi W, Fang Q, Zhu X, Norwood R A, Peyghambarian N 2014 Appl. Opt. 53 6554
Google Scholar
[3] Snitzer E, Po H, Hakimi F, Tumminelli R, McCollum B C 1988 Optical Fiber Sensors. 2 PD5
Google Scholar
[4] Nilsson J, Payne D N 2011 Science. 332 6032
Google Scholar
[5] 周朴, 许晓军, 刘泽金, 陈子伦, 陈金宝, 赵伊君 2008 激光与光电子学进展 45 37
Zhou P, Xu X J, Liu Z J, Chen Z L, Chen J B, Zhao Y J 2008 Laser & Optoelectronics Progress. 45 37
[6] Wirth C, Schmidt O, Tsybin I, Schreiber T, Eberhardt R, Limpert Y, Tünnermann A, Ludewigt K, Gowin M, Have E T, Jung M 2011 Opt. Lett. 36 3118
Google Scholar
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Google Scholar
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Google Scholar
[8] 潘雷雷, 张彬, 阴素芹, 张艳 2009 物理学报 58 8289
Google Scholar
Pan L L, Zhang B, Yin S Q, Zhang Y 2009 Acta. Phys. Sin. 58 8289
Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
Zhao X H, Gao Y, Xu M J, Duan W T, Yu H W 2008 Acta. Phys. Sin. 57 5027
Google Scholar
[14] 李尧, 吴涓, 林佶翔, 王雄飞, 朱辰 2009 激光技术 33 490
Li Y, Wu J, Lin J X, Wang X F, Zhu C 2009 Laser Technology 33 490
[15] 韩旭, 冯国英, 韩敬华, 张秋慧, 李尧, 张大勇 2009 光子学报 38 2468
Han X, Feng G Y, Han J H, Zhang Q Y, Li Y, Zhang D Y 2009 Acta. Photonica Sinica. 38 2468
[16] Zhang D, Zheng J F, Chen Y L, Li X L 2012 Annual Conference of Optics (laser) Societies of Heilongjiang, Jiangsu, Shandong, Henan and Jiangxi Provinces Zhengzhou, Henan, China, September 1, 2012 p16
[17] 盛泉, 司汉英, 张海伟, 张钧翔, 丁宇, 史伟, 姚建铨 2020 红外与激光工程 49 20200009
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Google Scholar
[19] Alig T, Bartels N, Allenspacher P, Balasa I, Böntgen T, Ristau D, Jensen L 2021 Opt. Express 29 14189
Google Scholar
[20] 朱文越, 钱仙妹, 饶瑞中, 王辉华 2019 红外与激光工程 48 1203002
Google Scholar
Zhu W Y, Qian X M, Rao R Z, Wang H H 2019 Infrar. Laser Eng. 48 1203002
Google Scholar
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Google Scholar
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Google Scholar
[22] 张月姣 2016 硕士学位论文 (哈尔滨: 哈尔滨工业大学)
Zhang Y J 2016 M. S. Thesis (Harbin: Harbin Institute of Technology) (in Chinese)
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Google Scholar
[24] Wang Y S, Feng Y G, Ma Y, Chang Z, Peng W J, Sun Y H, Gao Q S, Zhu R H, Tang C 2020 IEEE Photonics J. 12 1
Google Scholar
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Google Scholar
[26] 谢敬辉, 赵达尊, 阎吉祥 2005 物理光学教程 (第一版) (北京: 北京理工大学出版社) 第159—160页
Xie J H, Zhao D Z, Yan J X 2005 Phys. Optics Course (1st. Ed.) (Beijing: Beijing Institute of Technology Press) pp159–160 (in Chinese)
[27] 吕乃光 2006 傅里叶光学 (第二版) (北京: 机械工业出版社) 第121—122页
Lü N G 2006 Fourier Optices (2nd. Ed.) (Beijing: China Machine Press) pp121–122 (in Chinese)
[28] 王小林 张汉伟 史尘 段磊 奚小明 2021 基于SeeFiberLaser的光纤激光建模与仿真 (北京: 科学出版社) 第61—62页
Wang X L, Zhang H W, Shi C, Duan L, Xi X M 2021 Fiber Laser Simulation and Modeling Based on SeeFiberLaser (1st. Ed.) (Beijing: Science Press) pp61–62 (in Chinese)
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图 1 目标反射回光经大气传输耦合到光纤激光器中结构示意图
Figure 1. Schematic diagram of the structure of the target reflected light coupled to the fiber laser through atmospheric transmission.
图 2 大气传输网格划分和分段传输原理示意图
Figure 2. Schematic diagram of atmospheric transmission grid division and segmented transmission principle.
图 3 反射回光通过透镜耦合进入光纤示意图
Figure 3. Diagram of reflected light coupling through a lens into an optical fiber.
图 4 光纤激光器基本结构与边界条件示意图
Figure 4. Schematic diagram of basic structure and boundary conditions of fiber laser.
图 5 不同位置处的反射回光 (a) 目标回光激光光斑形态; (b) 经过大气传输后光斑形态; (c)透镜孔径内光斑形态; (d) 透镜焦面光斑形态; (e) 光纤端面处光斑; (f) 光纤纤芯耦合光斑
Figure 5. Reflected light at different locations: (a) The morphology of the laser spot of the target return light; (b) the pattern of light spots after atmospheric transmission; (c) the pattern of light spots in the aperture of the lens; (d) the morphology of focal spot of lens; (e) light spots on the end face of the optical fiber; (f) fiber core coupling spot.
图 6 光纤端面处反射回光功率和纤芯处接受到功率随传输距离的变化
Figure 6. Reflected power at the end face of the fiber and the received power at the core change with the transmission distance.
图 7 光轴偏移角度对耦合功率的影响
Figure 7. Effect of optical axis offset angle on coupling power.
图 8 光纤端面功率及耦合功率随光束中心位置偏移量的变化关系
Figure 8. Relationship of fiber end power and coupling power with the offset of beam center position.
图 9 发散角与纤芯耦合功率的关系
Figure 9. Relationship between divergence angle and core coupling power.
图 10 MOPA光纤激光器结构示意图
Figure 10. Schematic diagram of fiber laser structure of MOPA.
图 11 仿真结果 (a) 输出端增益光纤功率分布; (b) 光谱分布; (c) 中心轴向温度分布; (d) 径向横截面温度分布
Figure 11. Simulation results: (a) Output gain fiber power distribution; (b) spectral distribution; (c) central axial temperature distribution; (d) temperature distribution in radial cross section.
图 12 不同回光功率下激光功率和拉曼功率分布
Figure 12. Distribution of laser power and Raman power under different optical return power.
图 13 不同泵浦吸收系数下光纤径向横截面温度分布
Figure 13. Temperature distribution of fiber radial cross section under different pump absorption coefficients.
图 14 不同泵浦吸收系数下的信号光光谱, 内插图为掺镱光纤泵浦吸收系数1.5 dB@975 nm时的信号光光谱图
Figure 14. Signal light spectrum under different pump absorption coefficients. The inner illustration shows the signal light spectrum at the pump absorption coefficient of ytterbium-doped fiber 1.5 dB@975 nm.
图 15 输出光束质量因子与回光光束质量因子的关系
Figure 15. Relationship between the out light beam quality factor and the reflected light beam quality factor
表 1 仿真中使用的参数
Table 1. Parameters used in the simulation.
参数 数值 参数 数值 回光激光功率 Plaser/W 1000 泵浦光中心波长 λp/nm 976 高斯束腰半径 ω0/m 0.005 纤芯直径 rcore/μm 20 激光中心波长 λ/nm 1080 包层直径 rclad/μm 400 目标回光孔径 Robj/m 0.08 泵浦重叠因子 Γp 0.00774 大气传输距离 Zatm/m 500—3000 信号填充因子 Γs 1 大气相干长度 r0/m 0.0384 上能级粒子数寿命 τ/ms 0.85 大气透过率 Ttrans 0.095 光纤长度 L/m 20 通光孔径 Rlens/m 0.1 泵浦吸收系数 β/dB@976 nm 1.5—4.8 耦合透镜焦距 f/m 0.4 环境温度 T/℃ 25 光轴倾斜角度偏移量 θ/(°) 0—0.44 换热系数 κ/(W·m–2·K–1) 1200 光轴偏移位置偏移量 Δz/m X/Y: 0—0.06 纤芯直径 Rcore/μm 20 包层直径 Rclad/μm 400 
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[1] Koester C J, Snitzer E 1964 Appl. Opt. 3 1182
Google Scholar
[2] Shi W, Fang Q, Zhu X, Norwood R A, Peyghambarian N 2014 Appl. Opt. 53 6554
Google Scholar
[3] Snitzer E, Po H, Hakimi F, Tumminelli R, McCollum B C 1988 Optical Fiber Sensors. 2 PD5
Google Scholar
[4] Nilsson J, Payne D N 2011 Science. 332 6032
Google Scholar
[5] 周朴, 许晓军, 刘泽金, 陈子伦, 陈金宝, 赵伊君 2008 激光与光电子学进展 45 37
Zhou P, Xu X J, Liu Z J, Chen Z L, Chen J B, Zhao Y J 2008 Laser & Optoelectronics Progress. 45 37
[6] Wirth C, Schmidt O, Tsybin I, Schreiber T, Eberhardt R, Limpert Y, Tünnermann A, Ludewigt K, Gowin M, Have E T, Jung M 2011 Opt. Lett. 36 3118
Google Scholar
[7] 肖起榕, 田佳丁, 李丹, 齐天澄, 王泽晖, 于伟龙, 吴与伦, 闫平, 巩马理 2021 中国激光 48 1501004
Google Scholar
Xiao Q R, Tian J D, Li D, Qi T C, Wang Z H, Yu W L, Wu Y L, Yan P, Gong M L 2021 Chin. J. Lasers 48 1501004
Google Scholar
[8] 潘雷雷, 张彬, 阴素芹, 张艳 2009 物理学报 58 8289
Google Scholar
Pan L L, Zhang B, Yin S Q, Zhang Y 2009 Acta. Phys. Sin. 58 8289
Google Scholar
[9] Honea E, Afzal R S, Matthias S L, et al. 2016 Components and Packaging for Laser Systems II San Francisco, California, United States, April 22, 2016 p97300Y
[10] Chen, F, Ma, J, Wei, C, Zhu R, Zhou W C, Yuan Q, Pan S H, Zhang J Y, Wen Y Z, Dou J T 2017 Opt. Express. 25 32783
Google Scholar
[11] Huang Y S, Xiao Q R, Li D, Xin J T, Wang Z H, Tian J D, Wu Y L, Gong M L, Zhu L Q, Yan P 2021 Opt. Laser Technol. 133 106538
Google Scholar
[12] Carter A, Samson, B N, Tankala K, Machewirth D P, Khitrov V, Manyam U H, Gonthier F, Seguin F 2005 Laser-Induced Damage in Optical Materials Boulder Colorado, United States, February 21, 2005 p561
[13] 赵兴海, 高杨, 徐美健, 段文涛, 於海武 2008 物理学报 57 5027
Google Scholar
Zhao X H, Gao Y, Xu M J, Duan W T, Yu H W 2008 Acta. Phys. Sin. 57 5027
Google Scholar
[14] 李尧, 吴涓, 林佶翔, 王雄飞, 朱辰 2009 激光技术 33 490
Li Y, Wu J, Lin J X, Wang X F, Zhu C 2009 Laser Technology 33 490
[15] 韩旭, 冯国英, 韩敬华, 张秋慧, 李尧, 张大勇 2009 光子学报 38 2468
Han X, Feng G Y, Han J H, Zhang Q Y, Li Y, Zhang D Y 2009 Acta. Photonica Sinica. 38 2468
[16] Zhang D, Zheng J F, Chen Y L, Li X L 2012 Annual Conference of Optics (laser) Societies of Heilongjiang, Jiangsu, Shandong, Henan and Jiangxi Provinces Zhengzhou, Henan, China, September 1, 2012 p16
[17] 盛泉, 司汉英, 张海伟, 张钧翔, 丁宇, 史伟, 姚建铨 2020 红外与激光工程 49 20200009
Google Scholar
Sheng Q, Si H Y, Zhang H W, Zhang Y X, Ding Y, Shi W, Yao J Q 2020 Infrar. Laser Eng. 49 20200009
Google Scholar
[18] Chapman T, Michel P, Nicola D J M G, Berger R L, Whitman P K, Moody J D, Manes K R, Spaeth M L, Belyaev M A, Thomas C A, MacGowan B J 2019 J. Appl. Phys. 125 033101
Google Scholar
[19] Alig T, Bartels N, Allenspacher P, Balasa I, Böntgen T, Ristau D, Jensen L 2021 Opt. Express 29 14189
Google Scholar
[20] 朱文越, 钱仙妹, 饶瑞中, 王辉华 2019 红外与激光工程 48 1203002
Google Scholar
Zhu W Y, Qian X M, Rao R Z, Wang H H 2019 Infrar. Laser Eng. 48 1203002
Google Scholar
[21] 饶瑞中 2022 红外与激光工程 51 20210818
Google Scholar
Rao R Z 2022 Infrar. Laser Eng. 51 20210818
Google Scholar
[22] 张月姣 2016 硕士学位论文 (哈尔滨: 哈尔滨工业大学)
Zhang Y J 2016 M. S. Thesis (Harbin: Harbin Institute of Technology) (in Chinese)
[23] Xu Y, Fang Q, Qin Y, Meng X, Shi W 2015 A. O. 54 9419
Google Scholar
[24] Wang Y S, Feng Y G, Ma Y, Chang Z, Peng W J, Sun Y H, Gao Q S, Zhu R H, Tang C 2020 IEEE Photonics J. 12 1
Google Scholar
[25] Ren S, Ma P, Li W, Wang G, Chen Y, Song J, Liu W, Zhou P 2022 Nanomaterials. Basel. 12 2541
Google Scholar
[26] 谢敬辉, 赵达尊, 阎吉祥 2005 物理光学教程 (第一版) (北京: 北京理工大学出版社) 第159—160页
Xie J H, Zhao D Z, Yan J X 2005 Phys. Optics Course (1st. Ed.) (Beijing: Beijing Institute of Technology Press) pp159–160 (in Chinese)
[27] 吕乃光 2006 傅里叶光学 (第二版) (北京: 机械工业出版社) 第121—122页
Lü N G 2006 Fourier Optices (2nd. Ed.) (Beijing: China Machine Press) pp121–122 (in Chinese)
[28] 王小林 张汉伟 史尘 段磊 奚小明 2021 基于SeeFiberLaser的光纤激光建模与仿真 (北京: 科学出版社) 第61—62页
Wang X L, Zhang H W, Shi C, Duan L, Xi X M 2021 Fiber Laser Simulation and Modeling Based on SeeFiberLaser (1st. Ed.) (Beijing: Science Press) pp61–62 (in Chinese)
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