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产生单频激光的关键技术是建立一个单纵模运转的激光谐振腔,根据运行方式可分为行波腔和驻波腔。
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行波腔,采用较长的腔体,通过窄带滤波装置实现单纵模运转,典型装置如图1所示 [3]。采用额外的非泵浦掺铒光纤作为可饱和吸收体,当激光在此段光纤中干涉时引起驻波饱和效应,形成瞬态带通光栅滤波器,从而保证了稳定的单频激光运转。行波腔中无源可调谐滤波器可以提供粗波长选择,调谐范围比较宽。表1列出了基于行波腔结构的单频掺铒光纤激光器研究成果 [4-15]。
图 1 典型行波腔掺铒光纤激光器的原理示意图
Figure 1. Schematic diagram of a typical traveling wave cavity erbium-doped fiber laser
表 1 行波腔单频掺铒光纤激光器研究进展
Table 1. Research progress of single-frequency erbium-doped fiber lasers with traveling-wave cavity
Structure Fiber type Year Institution Wavelength/nm Power/mW Linewidth/kHz Ref. Traveling-wave cavity Phosphor-alumino-
silicate fiber1990 University of Southampton 1555 1 <60 [4] Silica fiber 1990 NTT Transmission Systems Laboratories 1549.3-1552.1 1.3 <1.4 [5] Silica fiber 1991 Telcordia Technologies 1525-1565 2 10 [6] Silica fiber 1991 Alcatel-Lucent 1528-1572 0.32 10 [7] Silica fiber 1991 AT&T Bell Laboratories 1530-1575 3 <5.5 [8] Silica fiber 1994 University of Southampton 1535 6.2 <0.95 [9] Silica fiber 2001 University of Southern California 1522-1562 10 0.75 [10] Silica fiber 2003 EXFO Electro-Optical Engineering 1510-1580 0.5 - [11] Silica fiber 2005 National Chiao Tung University 1482-1512 1.3 - [12] Silica fiber 2005 National Chiao Tung University 1480.6-1522.9 10 - [13] Phosphate fiber 2005 University of Arizona 1535 1000 - [14] Silica fiber 2008 Shanghai Jiao Tong University 1565 867 - [15] 1990年,英国南安普顿大学的Morkel等在环形腔中通过控制激光单向运转消除空间烧孔效应,首次实现了掺铒光纤的单频1555 nm激光输出 [4]。输出功率为1 mW、线宽小于60 kHz。1991年,美国Telcordia Technologies的Smith等报导了在腔内插入声光滤波器实现了高达40 nm范围连续可调的单频掺铒光纤激光输出,中心波长在1545 nm,输出功率2 mW,激光线宽为10 kHz [6]。由于行波腔对温度漂移和其他外界干扰的高灵敏度,激光模式不易稳定。
为改善行波腔掺铒单频激光器的跳模现象,可以通过引入可饱和吸收体来减少模式跳变。1994年,南安普顿大学的Cheng等人首次采用未泵浦的掺铒光纤作为可饱和吸收体实现稳定无跳模的单频掺铒光纤激光输出,中心波长为1535 nm,线宽为0.95 kHz,输出功率6.2 mW [9]。
此前的大部分报道都集中在C波段和部分L波段,而发展S波段的单频掺铒激光对于拓宽通信通道具有重要意义。2005年,National Chiao Tung University的Chien等人首次报导了S波段单频掺铒光纤环形腔激光器,可调谐范围覆盖1482~1512 nm,输出功率在1.3 mW [12]。同年该组人员将此波段单频掺铒光纤环形腔激光器输出功率提升到10 mW [13]。
此外还可以采用复合腔结构改善激光模式。复合腔激光器是由两个或者多个子腔组成,只允许一个满足所有子腔共振条件的激光纵模运转。为了实现这一目的,必须使各子腔之间不对称,即采用不同的腔长配置,从而延长激光的有效自由光谱范围,在过去的10多年里,有很多关于这一主题的报道 [16-23]。
但是受光纤中铒离子低掺杂浓度的制约,直接从环形腔输出的单频激光功率较低。直到2005年,美国亚利桑那大学的Polynkin等利用高掺铒磷酸盐光纤作为增益介质将环形腔单频激光器输出功率突破瓦量级,实现了700 mW输出功率下完全无跳模,但更高功率下仍有跳模发生 [14]。2008年,上海交通大学Yang等人在环形腔内加入放大结构获得了输出功率高达867 mW的单频激光 [15],这也是国内首次报导如此高功率的单频掺铒光纤激光器。
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根据结构区别,驻波腔分为分布反馈式(DFB)和分布布拉格反射式(DBR)两种腔型。
DFB结构是将光纤布拉格光栅(FBG)直接写入有源光纤中,在光栅区域的中间引入相位变化,如图2所示 [3]。该结构可以作为一个超窄光谱滤波器来实现单频运转。然而,一方面由于腔长较短,另一方面在高泵浦功率下,相移光纤光栅腔内存在着严重的热效应,导致光栅折射率发生变化,进而导致光栅失相,致使单频DFB光纤激光器输出功率有限。
图3显示了DBR单频光纤激光器的典型结构 [3],该激光腔由一对窄带FBG与一段掺铒光纤组合而成,具有结构简单、紧凑等优点。对于单频运转工作,掺铒光纤的长度通常限制在几厘米,同样要求光纤具有较高的增益系数。
近年来,国内华南理工大学、天津大学和国防科技大学多个课题组先后对DBR单频光纤激光器的研究进展作了综述性报道 [24-27],这里针对驻波腔单频掺铒光纤激光器研究进展作简单说明。表2列出了近年来基于驻波腔结构的单频掺铒光纤激光器的研究成果 [28-39]。
表 2 驻波腔单频掺铒光纤激光器研究进展
Table 2. Research progress of single-frequency erbium-doped fiber lasers with standing-wave cavity
Structure Fiber type Year Institution Wavelength/nm Power/mW Linewidth/kHz Ref. DBR Silica fiber 1991 United Technologies Research Center 1548 5 <47 [28] DBR Silica fiber 1994 United Technologies Research Center 1525-1557 3 - [29] DBR Phosphate fiber 2016 South China University of Technology 1527-1563 2.5 <0.7 [30] DBR Phosphate fiber 2017 South China University of Technology 1603 20 1.9 [31] DBR Phosphate fiber 2003 NP Photonics 1535 100 <2 [32] DBR Phosphate fiber 2004 NP Photonics 1560 >200 <2 [33] DBR Phosphate fiber 2005 University of Arizona 1535 1 900 - [34] DBR Phosphate fiber 2005 University of Arizona 1550 1600 - [35] DFB Phosphate photonic crystal fiber 2006 University of Arizona 1534 2300 - [36] DBR Phosphate fiber 2010 Shanghai Institute of Optics and
Fine Mechanics, CAS1535 100 <5 [37] DBR Phosphate fiber 2010 South China University of Technology 1535 306 1.6 [38] Linear cavity Silica fiber 2001 Electronics and Telecommunications
Research Institute1525-1565 0.08 <4.6 [39] 第一个DBR结构的单频掺铒光纤激光器早在1991年被演示[28],利用掺铒锗铝硅酸盐光纤作为增益介质,但受铒离子浓度制约,激光输出功率只有5 mW。在波长拓展方面,1994年,美国United Technologies Research Center的Ball等人通过对增益光纤施加纵向应力实现了32 nm的可调谐单频激光输出,覆盖1525~1557 nm波长范围 [29]。2017年,华南理工大学Yang等人报道了利用1.6 cm铒镱共掺磷酸盐光纤作为增益介质的DBR单频激光器,通过优化光栅参数获得了输出功率为20 mW、线宽为1.9 kHz的1603 nm单频激光,这也是首次实现1600 nm以上波长的单频掺铒光纤激光器 [31]。
驻波腔结构单频掺铒光纤激光器的功率提升主要得益于铒镱共掺磷酸盐光纤的发明。2003年,美国NP Photonics公司Spiegeberg等基于高浓度铒镱共掺磷酸盐光纤首次报道了百毫瓦功率量级的单频掺铒光纤激光器 [32],工作波长为1535 nm,线宽小于2 kHz,并于次年将单频激光功率提升到200 mW [33]。随着共掺双包层磷酸盐光纤和包层泵浦技术的发展,驻波腔单频掺铒光纤激光器输出功率提升到瓦量级[34-35]。
Research progress of high-power single-frequency erbium-doped fiber laser technology (Invited)
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摘要: 近年来,在相干探测、激光雷达、激光冷却以及引力波探测等领域应用需求的驱动下,窄线宽、低噪声的高功率单频掺铒光纤激光技术成为国内外光纤激光技术领域的研究热点。简要介绍了近些年高功率单频掺铒光纤激光技术的研究进展,包括单频掺铒光纤激光器和高功率单频掺铒光纤放大器,分析了高功率单频掺铒光纤激光的发展趋势和面临的挑战,并对下一步的发展方向进行了展望。Abstract: In recent years, high-power single-frequency (SF) erbium-doped fiber lasers with narrow linewidth and low noise have been intensively studied, driven by application requirements in the fields of coherent detection, lidar, laser cooling and gravitational wave detection. The research progresses of high-power SF erbium-doped fiber lasers were reviewed in this paper, including SF erbium-doped fiber lasers and high-power SF erbium-doped fiber amplifiers. The development trend and challenges of the high-power SF erbium-doped fiber lasers were analyzed, and the next development direction was prospected.
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表 1 行波腔单频掺铒光纤激光器研究进展
Table 1. Research progress of single-frequency erbium-doped fiber lasers with traveling-wave cavity
Structure Fiber type Year Institution Wavelength/nm Power/mW Linewidth/kHz Ref. Traveling-wave cavity Phosphor-alumino-
silicate fiber1990 University of Southampton 1555 1 <60 [4] Silica fiber 1990 NTT Transmission Systems Laboratories 1549.3-1552.1 1.3 <1.4 [5] Silica fiber 1991 Telcordia Technologies 1525-1565 2 10 [6] Silica fiber 1991 Alcatel-Lucent 1528-1572 0.32 10 [7] Silica fiber 1991 AT&T Bell Laboratories 1530-1575 3 <5.5 [8] Silica fiber 1994 University of Southampton 1535 6.2 <0.95 [9] Silica fiber 2001 University of Southern California 1522-1562 10 0.75 [10] Silica fiber 2003 EXFO Electro-Optical Engineering 1510-1580 0.5 - [11] Silica fiber 2005 National Chiao Tung University 1482-1512 1.3 - [12] Silica fiber 2005 National Chiao Tung University 1480.6-1522.9 10 - [13] Phosphate fiber 2005 University of Arizona 1535 1000 - [14] Silica fiber 2008 Shanghai Jiao Tong University 1565 867 - [15] 表 2 驻波腔单频掺铒光纤激光器研究进展
Table 2. Research progress of single-frequency erbium-doped fiber lasers with standing-wave cavity
Structure Fiber type Year Institution Wavelength/nm Power/mW Linewidth/kHz Ref. DBR Silica fiber 1991 United Technologies Research Center 1548 5 <47 [28] DBR Silica fiber 1994 United Technologies Research Center 1525-1557 3 - [29] DBR Phosphate fiber 2016 South China University of Technology 1527-1563 2.5 <0.7 [30] DBR Phosphate fiber 2017 South China University of Technology 1603 20 1.9 [31] DBR Phosphate fiber 2003 NP Photonics 1535 100 <2 [32] DBR Phosphate fiber 2004 NP Photonics 1560 >200 <2 [33] DBR Phosphate fiber 2005 University of Arizona 1535 1 900 - [34] DBR Phosphate fiber 2005 University of Arizona 1550 1600 - [35] DFB Phosphate photonic crystal fiber 2006 University of Arizona 1534 2300 - [36] DBR Phosphate fiber 2010 Shanghai Institute of Optics and
Fine Mechanics, CAS1535 100 <5 [37] DBR Phosphate fiber 2010 South China University of Technology 1535 306 1.6 [38] Linear cavity Silica fiber 2001 Electronics and Telecommunications
Research Institute1525-1565 0.08 <4.6 [39] -
[1] Bellemare A. Continuous-wave silica-based erbium-doped fiber lasers [J]. Progress in Quantum Electronics, 2003, 27(4): 211-266. doi: 10.1016/S0079-6727(02)00025-3 [2] Wagener J L, Wysocki P F, Digonnet M J F, et al. Effects of concentration and clusters in erbium-doped fiber lasers [J]. Optics Letters, 1993, 18(23): 2014-2016. doi: 10.1364/OL.18.002014 [3] Yang Z, Li C, Xu S, et al. Single-Frequency Fiber Lasers[M]. Singapore: Springer Nature, 2019. [4] Morkel P R, Cowle G J, Payne D N. Travelling-wave erbium fiber ring laser with 60 kHz linewidth [J]. Electronics Letters, 1990, 26(10): 632-634. doi: 10.1049/el:19900414 [5] Iwatsuki K, Okamura H, Saruwatari M. Wavelength-tunable single-frequency and single-polarisation Er-doped fiber ring-laser with 1.4 kHz linewidth [J]. Electronics Letters, 1990, 26(24): 2033-2035. doi: 10.1049/el:19901312 [6] Smith D A, Maeda M W, Johnson J J, et al. Acoustically tuned erbium-doped fiber ring laser [J]. Optics Letters, 1991, 16(6): 387-389. doi: 10.1364/OL.16.000387 [7] Schmuck H, Pfeiffer T, Veith G. Widely tunable narrow linewidth erbium doped fiber ring laser [J]. Electronics Letters, 1991, 27(23): 2117-2119. [8] Zyskind J L, Sulhoff J W, Sun Y, et al. Singlemode diode-pumped tunable erbium-doped fiber laser with linewidth less than 5.5 kHz [J]. Electronics Letters, 1991, 27(23): 2148-2149. doi: 10.1049/el:19911330 [9] Cheng Y, Kringlebotn J T, Loh W H, et al. Stable single-frequency traveling-wave fiber loop laser with integral saturable-absorber-based tracking narrow-band filter [J]. Optics Letters, 1995, 20(8): 875-877. doi: 10.1364/OL.20.000875 [10] Song Y W, Havstad S A, Starodubov D, et al. 40-nm-wide tunable fiber ring laser with single-mode operation using a highly stretchable FBG [J]. IEEE Photonics Technology Letters, 2001, 13(11): 1167-1169. doi: 10.1109/68.959352 [11] Chen H X, Babin F, Leblanc M, et al. Widely tunable single-frequency erbium-doped fiber lasers [J]. IEEE Photonics Technology Letters, 2003, 15(2): 185-187. doi: 10.1109/LPT.2002.806833 [12] Chien H C, Yeh C H, Lee C C, et al. A tunable and single-frequency s-band erbium fiber laser with saturable-absorber-based autotracking filter [J]. Optics Communications, 2005, 250(1): 163-167. [13] Yeh C H, Lin M C, Chi S. Stabilized and wavelength-tunable s-band erbium-doped fiber ring laser with single-longitudinal-mode operation [J]. Optics Express, 2005, 13(18): 6828-6832. doi: 10.1364/OPEX.13.006828 [14] Polynkin A, Polynkin P, Mansuripur M, et al. Single-frequency fiber ring laser with 1 W output power at 1.5 µm [J]. Optics Express, 2005, 13(8): 3179-3184. doi: 10.1364/OPEX.13.003179 [15] Yang X X, Zhan L, Shen Q S, et al. High-power single-longitudinal-mode fiber laser with a ring Fabry-Perot resonator and a saturable absorber [J]. IEEE Photonics Technology Letters, 2008, 20(9-12): 879-881. [16] Zhang J L, Yue C Y, Schinn G W, et al. Stable single-mode compound-ring erbium-doped fiber laser [J]. Journal of Lightwave Technology, 1996, 14(1): 104-109. doi: 10.1109/50.476143 [17] Lee C C, Chi S. Single-longitudinal-mode operation of a grating-based fiber-ring laser using self-injection feedback [J]. Optics Letters, 2000, 25(24): 1774-1776. doi: 10.1364/OL.25.001774 [18] Lee C C, Chen Y K, Liaw S K. Single-longitudinal-mode fiber laser with a passive multiple-ring cavity and its application for video transmission [J]. Optics Letters, 1998, 23(5): 358-360. doi: 10.1364/OL.23.000358 [19] Xin Z, Ning Hua Z, Liang X, et al. Stabilized and tunable single-frequency erbium-doped fiber ring laser employing external injection locking [J]. Journal of Lightwave Technology, 2007, 25(4): 1027-1033. doi: 10.1109/JLT.2007.891458 [20] Yeh C H, Huang T T, Chien H C, et al. Tunable S-band erbium-doped triple-ring laser with single-longitudinal-mode operation [J]. Optics Express, 2007, 15(2): 382-386. doi: 10.1364/OE.15.000382 [21] Pan S, Yao J. A Wavelength-tunable single-longitudinal-mode fiber ring laser with a large sidemode suppression and improved stability [J]. IEEE Photonics Technology Letters, 2010, 22(6): 413-415. doi: 10.1109/LPT.2010.2040996 [22] Salehiomran A, Rochette M. An all-pole-type cavity based on smith predictor to achieve single longitudinal mode fiber lasers [J]. IEEE Photonics Technology Letters, 2013, 25(21): 2141-2144. doi: 10.1109/LPT.2013.2282353 [23] Feng T, Yan F, Peng W, et al. A high stability wavelength-tunable narrow-linewidth and single-polarization erbium-doped fiber laser using a compound-cavity structure [J]. Laser Physics Letters, 2014, 11(4): 045101. doi: 10.1088/1612-2011/11/4/045101 [24] Yang C, Cen X, Xu S, et al. Research progress of single-frequency fiber laser [J]. Acta Optica Sinica, 2021, 41(1): 0114002. (in Chinese) doi: 10.3788/AOS202141.0114002 [25] Yang C, Xu S, Li C, et al. Research progress of 1.5 μm-band CW single-frequency fiber laser [J]. Scientia Sinica Chimica, 2013, 43(11): 1407-1417. (in Chinese) doi: 10.1360/032013-292 [26] Fu S J, Shi W, Feng Y, et al. Review of recent progress on single-frequency fiber lasers invited [J]. Journal of the Optical Society of America B-Optical Physics, 2017, 34(3): A49-A62. doi: 10.1364/JOSAB.34.000A49 [27] Lai W, Ma P, Xiao H, et al. High-power narrow-linewidth fiber laser technology [J]. High Power Laser and Particle Beams, 2020, 32(12): 121001. (in Chinese) doi: 10.11884/HPLPB202032.200186 [28] Ball G A, Morey W W, Glenn W H. Standing-wave monomode erbium fiber laser [J]. IEEE Photonics Technology Letters, 1991, 3(7): 613-615. doi: 10.1109/68.87930 [29] Ball G A, Morey W W. Compression-tuned single-frequency Bragg grating fiber laser [J]. Optics Letters, 1994, 19(23): 1979-1981. doi: 10.1364/OL.19.001979 [30] Zhang Y N, Zhang Y F, Zhao Q L, et al. Ultra-narrow linewidth full C-band tunable single-frequency linear-polarization fiber laser [J]. Optics Express, 2016, 24(23): 26209-26214. doi: 10.1364/OE.24.026209 [31] Yang C S, Guan X C, Lin W, et al. Efficient 1.6 μm linearly-polarized single-frequency phosphate glass fiber laser [J]. Optics Express, 2017, 25(23): 29078-29085. doi: 10.1364/OE.25.029078 [32] Spiegelberg C, Geng J, Hu Y, et al. Compact 100 mW fiber laser with 2 kHz linewidth [C]// Optical Fiber Communications Conference, 2003, 3: PD45-P1. [33] Spiegelberg C, Geng J H, Hu Y D, et al. Low-noise narrow-linewidth fiber laser at 1550 nm (June 2003) [J]. Journal of Lightwave Technology, 2004, 22(1): 57-62. doi: 10.1109/JLT.2003.822208 [34] Polynkin P, Polynkin A, Mansuripur M, et al. Single-frequency laser oscillator with watts-level output power at 1.5 μm by use of a twisted-mode technique [J]. Optics Letters, 2005, 30(20): 2745-2747. doi: 10.1364/OL.30.002745 [35] Qiu T, Suzuki S, Schulzgen A, et al. Generation of watt-level single-longitudinal-mode output from cladding-pumped short fiber lasers [J]. Optics Letters, 2005, 30(20): 2748-2750. doi: 10.1364/OL.30.002748 [36] Schulzgen A, Li L, Temyanko V L, et al. Single-frequency fiber oscillator with watt-level output power using photonic crystal phosphate glass fiber [J]. Optics Express, 2006, 14(16): 7087-7092. doi: 10.1364/OE.14.007087 [37] Pan Z, Cai H, Meng L, et al. Single-frequency phosphate glass fiber laser with 100-mw output power at 1535 nm and its polarization characteristics [J]. Chinese Optics Letters, 2010, 8(1): 52-54. doi: 10.3788/COL20100801.0052 [38] Xu S H, Yang Z M, Liu T, et al. An efficient compact 300 mW narrow-linewidth single frequency fiber laser at 1.5 μm [J]. Optics Express, 2010, 18(2): 1249-1254. doi: 10.1364/OE.18.001249 [39] Chang S H, Hwang I K, Kim B Y, et al. Widely tunable single-frequency Er-doped fiber laser with long linear cavity [J]. IEEE Photonics Technology Letters, 2001, 13(4): 287-289. doi: 10.1109/68.917827 [40] Kaneda Y, Hu Y, Spiegelberg C, et al. Single-frequency, all-fiber Q-switched laser at 1550 nm[C]// Proceedings of the Advanced Solid-State Photonics (TOPS), 2004. [41] Zhou R, Shi W, Petersen E, et al. Transform-limited, injection seeded, Q-switched, ring cavity fiber laser [J]. Journal of Lightwave Technology, 2012, 30(16): 2589-2595. doi: 10.1109/JLT.2012.2201446 [42] Wan H D, Wu Z W, Sun X H. A pulsed single-longitudinal-mode fiber laser based on gain control of pulse-injection-locked cavity [J]. Optics Laser Technology, 2013, 48: 167-170. doi: 10.1016/j.optlastec.2012.09.029 [43] Shi W, Leigh M A, Zong J, et al. High-power all-fiber-based narrow-linewidth single-mode fiber laser pulses in The C-Band and frequency conversion to THz generation [J]. IEEE Journal of Selected Topics in Quantum Electronics, 2009, 15(2): 377-384. doi: 10.1109/JSTQE.2008.2010234 [44] Leigh M, Shi W, Zong J, et al. High peak power single frequency pulses using a short polarization-maintaining phosphate glass fiber with a large core [J]. Applied Physics Letters, 2008, 92(18): 1-3. [45] Shi W, Petersen E B, Leigh M, et al. High SBS-threshold single-mode single-frequency monolithic pulsed fiber laser in the C-band [J]. Opt Express, 2009, 17(10): 8237-8245. doi: 10.1364/OE.17.008237 [46] Shi W, Petersen E B, Yao Z D, et al. Kilowatt-level stimulated-Brillouin-scattering-threshold monolithic transform-limited 100 ns pulsed fiber laser at 1530 nm [J]. Optics Letters, 2010, 35(14): 2418-2420. doi: 10.1364/OL.35.002418 [47] Petersen E, Shi W, Chavez-pirson A, et al. High peak-power single-frequency pulses using multiple stage, large core phosphate fibers and preshaped pulses [J]. Applied Optics, 2012, 51(5): 531-534. doi: 10.1364/AO.51.000531 [48] Liu Y, Liu J Q, Chen W B. Eye-safe, single-frequency pulsed all-fiber laser for Doppler wind lidar [J]. Chinese Optics Letters, 2011, 9(9): 090604. [49] Lee W, Geng J, Jiang S, et al. 1.8 mJ, 3.5 kW single-frequency optica pulses at 1572 nm generated from an all-fiber MOPA system [J]. Optics Letters, 2018, 43(10): 2264-2267. doi: 10.1364/OL.43.002264 [50] Zhang X, Diao W F, Liu Y, et al. Eye-safe single-frequency single-mode polarized all-fiber pulsed laser with peak power of 361 W [J]. Applied Optics, 2014, 53(11): 2465-2469. doi: 10.1364/AO.53.002465 [51] Ball G A, Holton C E, Hullallen G, et al. 60-mW 1.5 μm single-frequency low-noise fiber laser MOPA [J]. IEEE Photonics Technology Letters, 1994, 6(2): 192-194. doi: 10.1109/68.275425 [52] Pan J J, Shi Y. 166-mW single-frequency output power interactive fiber lasers with low noise [J]. IEEE Photonics Technology Letters, 1999, 11(1): 36-38. doi: 10.1109/68.736382 [53] Jeong Y, Salm J K, Richardson D J, et al. Seeded erbium/ytterbium codoped fiber amplifier source with 87 W of single-frequency output power [J]. Electronics Letters, 2003, 39(24): 1717-1719. doi: 10.1049/el:20031110 [54] Alam S U, Wixey R, Hickey L, et al. High power, single-mode, single-frequency DFB fiber laser at 1550 nm in MOPA configuration[C]//Proceedings of the Conference on Lasers and Electro-Optics, 2004 (CLEO), F, 2004. [55] Alegria C, Jeong Y, Codemard C, et al. 83-W single-frequency narrow-linewidth MOPA using large-core erbium-ytterbium co-doped fiber [J]. IEEE Photonics Technology Letters, 2004, 16(8): 1825-1827. doi: 10.1109/LPT.2004.830520 [56] Jeong Y, Sahu J K, Soh D B S, et al. High-power tunable single-frequency single-mode erbium: ytterbium codoped large-core fiber master-oscillator power amplifier source [J]. Optics Letters, 2005, 30(22): 2997-2999. doi: 10.1364/OL.30.002997 [57] Dubinskii M, Zhang J, Kudryashov I. Single-frequency, Yb-free, resonantly cladding-pumped large mode area Er fiber amplifier for power scaling [J]. Applied Physics Letters, 2008, 93(3): 1-3. [58] Yang C S, Xu S H, Mo S P, et al. 10.9 W kHz-linewidth one-stage all-fiber linearly-polarized MOPA Laser at 1560 nm [J]. Optics Express, 2013, 21(10): 12546-12551. doi: 10.1364/OE.21.012546 [59] Steinke M, Croteau A, Pare C, et al. Co-seeded Er3+: Yb3+ single frequency fiber amplifier with 60 w output power and over 90% TEM00 content [J]. Optics Express, 2014, 22(14): 16722-16730. doi: 10.1364/OE.22.016722 [60] Bai X L, Sheng Q, Zhang H W, et al. High-power all-fiber single-frequency erbium-ytterbium co-doped fiber master oscillator power amplifier [J]. IEEE Photonics Journal, 2015, 7(6): 6. [61] Creeden D, Pretorius H, Limongelli J, et al. Single frequency 1560 nm Er: Yb fiber amplifier with 207 W output power and 50.5% slope efficiency[C]//Proceedings of the Conference on Fiber Lasers XIII -Technology, Systems, and Applications, F, 2016. [62] De Varona O, Fittkau W, Booker P, et al. Single-frequency fiber amplifier at 1.5 μm with 100 W in the linearly-polarized TEM00 Mode for next-generation gravitational wave detectors [J]. Optics Express, 2017, 25(21): 24880-24892. doi: 10.1364/OE.25.024880 [63] Yang C S, Guan X C, Zhao Q L, et al. 15 W high OSNR kHz-linewidth linearly-polarized all-fiber single-frequency MOPA a 1.6 μm [J]. Optics Express, 2018, 26(10): 12863-12869. doi: 10.1364/OE.26.012863 [64] Guan X C, Zhao Q L, Lin W, et al. High-efficiency and high-power single-frequency fiber laser at 1.6 μm based on cascaded energy-transfer pumping [J]. Photonics Research, 2020, 8(3): 414-420. doi: 10.1364/PRJ.383174 [65] Xue M Y, Gao C X, Niu L Q, et al. A 51.3 W, sub-kHz-linewidth linearly polarized all-fiber laser at 1560 nm [J]. Laser Physics, 2020, 30(3): 035104. doi: 10.1088/1555-6611/ab67ce [66] Darwich D, Bardin Y V, Goeppner M, et al. Ultralow-intensity noise, 10 W all-fiber single-frequency tunable laser system around 1550 nm [J]. Applied Optics, 2021, 60(27): 8550-8555. doi: 10.1364/AO.435274 [67] Kuhn V, Kracht D, Neumann J, et al. Er-doped single-frequency photonic crystal fiber amplifier with 70 W of output power for gravitational wave detection[C]//Proceedings of the Conference on Fiber Lasers IX - Technology, Systems, and Applications, 2012. [68] Fujisaki A, Matsushita S, Kasai K, et al. An 11.6 W output, 6 kHz linewidth, single-polarization EDFA-MOPA system with a 13C2H2 frequency stabilized fiber laser [J]. Optics Express, 2015, 23(2): 1081-1087. doi: 10.1364/OE.23.001081 [69] Dong J Y, Zeng X, Cui S Z, et al. More than 20 W fiber-based continuous-wave single frequency laser at 780 nm [J]. Optics Express, 2019, 27(24): 35362-35367. doi: 10.1364/OE.27.035362 [70] Alam S, Yla-jarkko K H, Grudinin A B. High power, single frequency DFB fiber laser with low relative intensity noise[C]// Proceedings of the 2003 Conference on Lasers and Electro-Optics Europe (CLEO/Europe 2003) (IEEE Cat No03 TH8666), 2003: 618. [71] De Varona O, Steinke M, Neumann J, et al. All-fiber, single-frequency, and single-mode Er3+: Yb3+ fiber amplifier at 1556 nm core-pumped at 1018 nm [J]. Optics Letters, 2018, 43(11): 2632-2635. doi: 10.1364/OL.43.002632 [72] Wang S, Liu Z, Zhao Z, et al. 18 W Single-frequency 1550 nm Er: Yb co-doped fiber amplifier cladding-pumping at 1018 nm [J]. Optics Communications, 2020, 464: 125498. doi: 10.1016/j.optcom.2020.125498 [73] Kuhn V, Kracht D, Neumann J, et al. Dependence of Er: Yb-codoped 1.5 μm amplifier on wavelength-tuned auxiliary seed signal at 1 μm wavelength [J]. Optics Letters, 2010, 35(24): 4105-4107. doi: 10.1364/OL.35.004105 [74] Sobon G, Sliwinska D, Kaczmarek P, et al. Er/Yb co-doped fiber amplifier with wavelength-tuned Yb-band ring resonator [J]. Optics Communications, 2012, 285(18): 3816-3819. doi: 10.1016/j.optcom.2012.05.018 [75] Dubinskii M, Zhang J, Ter-mikirtychev V. Record-efficient, resonantly-pumped, Er-doped single mode fiber amplifier [J]. Electronics Letters, 2009, 45(8): 400-401. doi: 10.1049/el.2009.0505 [76] Supradeepa V R, Nicholson J W. Power scaling of high-efficiency 1.5 μm cascaded Raman fiber lasers [J]. Optics Letters, 2013, 38(14): 2538-2541. doi: 10.1364/OL.38.002538