[1] [1] Snitzer E. Optical maser action of Nd+3 in a barium crown glass［J］. Physical Review Letters, 1961, 7(12): 444-446.

[2] [2] Koester C J, Snitzer E. Amplification in a fiber laser［J］. Applied Optics, 1964, 3(10): 1182-1186.

[3] [3] Poole S B, Payne D N, Fermann M E. Fabrication of low-loss optical fibres containing rare-earth ions［J］. Electronics Letters, 1985, 21(17): 737-738.

[4] [4] Desurvire E, Simpson J R, Becker P C. High-gain erbium-doped traveling-wave fiber amplifier［J］. Optics Letters, 1987, 12(11): 888-890.

[5] [5] Snitzer E, Po H, Hakimi F, et al. Double clad, offset core Nd fiber laser［C］. New Orleans: Optical Fiber Sensors, 1988: PD5.

[6] [6] Hanna D C, Percival R M, Perry I R, et al. An ytterbium-doped monomode fibre laser: broadly tunable operation from 1.010 μm to 1.162 μm and three-level operation at 974 nm［J］. Journal of Modern Optics, 1990, 37(4): 517-525.

[7] [7] Gapontsev V, Samartsev I, Zayats A, et al. Laser-diode pumped Yb-doped single-mode tunable fibre lasers［C］. Proc of Conf Adv Solid State Lasers, Hilton Head, NC, paper WC1-1, 1991: 214.

[8] [8] IPG Photonics offers world′s first 10 kW single-mode production laser［OL］. (2009-06-17). http://www.laserfocusworld.com/articles/2009/06/ipg-photonics-offers-worlds-first-10-kw-single-mode-production-laser.html.

[9] [9] Ferin A, Gapontsev V, Fomin V, et al. 17 kW CW laser with 50 μm delivery［C］. Chengdu: 6th International Symposium on High-Power Fiber Lasers and Their Applications, 2012.

[10] [10] Jeong Y, Sahu J, Payne D, et al. Ytterbium-doped large-core fiber laser with 1 kW continuous-wave output power［J］. Electronics Letters, 2004, 40(8): 470-472.

[11] [11] Jeong Y C, Boyland A J, Sahu J K, et al. Multi-kilowatt single-mode ytterbium-doped large-core fiber laser［J］. Journal of the Optical Society of Korea, 2009, 13(4): 416-422.

[12] [12] Wirth C, Schmidt O, Kliner A, et al. High-power tandem pumped fiber amplifier with an output power of 2.9 kW［J］. Optics Letters, 2011, 36(16): 3061-3063.

[13] [13] Ramachandran S, Khitrov V, Minelly J D, et al. 3 kW single-mode direct diode-pumped fiber laser［C］. SPIE, 2014, 8961: 89610V.

[14] [14] Peterka P, Kasik I, Matejec V, et al. Novel method for end-pumping of double-clad fiber amplifiers: principle and tailoring the cross section［J］. Biological Trace Element Research, 2005, 75(1-3): 29-41.

[15] [15] Peterka P, Kaík I, Matějec V, et al. Experimental demonstration of novel end-pumping method for double-clad fiber devices［J］. Optics Letters, 2006, 31(22): 3240-3242.

[16] [16] Digiovanni D J, Stentz A J. Tapered fiber bundles for coupling light into and out of cladding-pumped fiber devices: US5864644［P］. 1999-01-26.

[17] [17] Fidric B G, Dominic V G, Sanders S. Optical couplers for multimode fibers: US6434302［P］. 2002-08-13.

[18] [18] Gonthier F, Martineau L, Seguin F, et al. Optical coupler comprising multimode fibers and method of making the same: US7046875［P］. 2006-06-04.

[19] [19] Kosterin A, Temyanko V, Fallahi M, et al. Tapered fiber bundles for combining high-power diode lasers［J］. Applied Optics, 2004, 43(19): 3893-3900.

[20] [20] Wang B, Mies E. Review of fabrication techniques for fused fiber components for fiber lasers［C］. SPIE, 2009, 7195: 71950A.

[21] [21] Wetter A, Faucher M, Lovelady M, et al. Tapered fused-bundle splitter capable of 1 kW CW operation［C］. SPIE, 2007, 6453: 64530I.

[22] [22] Zhou H, Chen Z, Zhou X, et al. All-fiber 7×1 pump combiner for high power fiber laser［J］. Optics Communications, 2015, 347: 137-140.

[23] [23] Xiao Q, Yan P, He J, et al. Tapered fused fiber bundle coupler capable of 1 kW laser combining and 300 W laser splitting［J］. Laser Physics, 2011, 21(8): 1415-1419.

[24] [24] Xiao Q, Ren H, Chen X, et al. Tapered fiber bundle 7×1 end-pumping coupler capable of high power CW operation［J］. IEEE Photonics Technology Letters, 2013, 25(24): 2442-2445.

[25] [25] Xiao Q, Huang Y, Sun J, et al. Research on multi-kilowatts level tapered fiber bundle N×1 pumping combiner for high power fiber laser［J］. Frontiers of Optoelectronics, 2016, 9(2): 301-305.

[26] [26] Nielsen M D, Srensen M H, Liem A, et al. High-power PCF-based pump combiners［C］. SPIE, 2007, 6453: 64532C.

[27] [27] Wieduwilt T, Dellith J, Talkenberg F, et al. Reflectivity enhanced refractive index sensor based on a fiber-integrated Fabry-Perot microresonator［J］. Optics Express, 2014, 22(21): 25333-25346.

[28] [28] Noordegraaf D, Nielsen M D, Skovgaard P M, et al. Pump combiner for air-clad fiber with PM single-mode signal feed-through［C］. Maryland: Conference on Lasers & Electro-optics, 2009.

[29] [29] Noordegraaf D, Maack M, Skovgaard P M W, et al. 7+1 to 1 pump/signal combiner for air-clad fiber with 15 m MFD PM single-mode signal feed-through［C］. SPIE, 2010, 7580: 75801A.

[30] [30] Ward B G, Jr, Sipes D L, Tafoya J D. A monolithic pump signal multiplexer for air-clad photonic crystal fiber amplifiers［C］. SPIE, 2010, 7580: 75801C.

[31] [31] Kim J K, Hagemann C, Schreiber T, et al. Monolithic all-glass pump combiner scheme for high-power fiber laser systems［J］. Optics Express, 2010, 18(12): 13194-13203.

[32] [32] Ramachandran S, Sipes D L, Tafoya J D, et al. High-power monolithic fiber amplifiers based on advanced photonic crystal fiber designs［C］. SPIE, 2014, 8961: 896114.

[33] [33] Glebov A L, Leisher P O, Boullet J, et al. Multi-100 W class, fully integrated, monolithic ytterbium-doped photonic-crystal fiber amplifier module［C］. SPIE, 2016, 9730: 97300Q.

[34] [34] Weber T, Lüthy W, Weber H. Side-pumped fiber laser［J］. Applied Physics B: Lasers and Optics, 1996, 63(2): 131-134.

[35] [35] Ripin D, Goldberg L. High efficiency side-coupling of light into optical fibres using imbedded V-grooves［J］. Electronics Letters, 1995, 31(25): 2204-2205.

[36] [36] Li C, Shen D, Song J, et al. Analysis of high-power double-clad fiber lasers side-pumped by multiple diode-lasers in V-groove configuration［C］. The Pacific Rim Conference on Lasers and Electro-Optics, 1999, 3: 805-806.

[37] [37] Snell K J, Setzler S D. Multiple emitter side pumping method and apparatus for fiber lasers: US6801550［P］. 2004-10-05.

[38] [38] Koplow J P, Goldberg L, Kliner D A V. Compact 1-W Yb-doped double-cladding fiber amplifier using V-groove side-pumping［J］. IEEE Photonics Technology Letters, 1998, 10(6): 793-795.

[39] [39] Koplow J P, Moore S W, Kliner D A V. A new method for side pumping of double-clad fiber sources［J］. IEEE Journal of Quantum Electronics, 2003, 39(4): 529-540.

[40] [40] Moore S W, Koplow J P, Hansen A, et al. Embedded-mirror side pumping of double-clad fiber lasers and amplifiers［C］. California: Conference on Lasers & Electro-Optics, 2008: 870-871.

[41] [41] Hageman W B, Chen Y, Bass M, et al. Diode side pumping of a gain guided, index anti-guided large mode area neodymium fiber laser［C］. San Diego: Advanced Solid-State Photonics, 2010.

[42] [42] Hamamatsu Photonics K. The fiber disk laser explained［J］. Nature Photonics, 2006: 14-15.

[43] [43] Herda R, Liem A, Schnabel B, et al. Efficient side-pumping of fibre lasers using binary gold diffraction gratings［J］. Electronics Letters, 2003, 39(3): 276-277.

[44] [44] Zhang F, Wang C, Geng R, et al. Novel grating couplers for diode-bars multi-point side-pumping double-clad fiber［J］. Optics Communications, 2007, 279(2): 346-355.

[45] [45] Huang C W, Huang D W, Chang C L, et al. Demonstration of side coupling between high power laser diode array and double-clad fiber using sub-wavelength grating［C］. Maryland: Lasers & Electro-Optics, 2011: 1-2.

[46] [46] Huang C W, Chang C L, Jheng D Y, et al. Symmetrically side-pumped 10-W ytterbium-doped fiber laser by sub-wavelength grating coupler［C］. Munich: The European Conference on Lasers and Electro-Optics, 2011.

[47] [47] Lin S L, Lee Y W, Hsu K Y, et al. Design of resonantly side-pumped 1645-nm Er:YAG crystal fiber lasers with grating couplers［C］. Kyoto: Conference on Lasers and Electro-Optics Pacific Rim, 2013: 1-2.

[48] [48] Hakimi F, Hakimi H. New side coupling method for double-clad fiber amplifiers［C］. Maryland: Conference on Lasers & Electro-Optics, 2001: 116.

[49] [49] Ou P, Yan P, Gong M, et al. Coupling efficiency of angle-polished method for side-pumping technology［J］. Optical Engineering, 2004, 43(4): 816-821.

[50] [50] Ou P, Yan P, Gong M, et al. Multi-coupler side-pumped Yb-doped double-clad fibre laser and pump light leakage at coupler［J］. Electronics Letters, 2004, 40(7): 418-419.

[51] [51] Xiao Q R, Yan P, Yin S, et al. 100 W ytterbium-doped monolithic fiber laser with fused angle-polished side-pumping configuration［J］. Laser Physics Letters, 2010, 8(2): 125-129.

[52] [52] Xiao Q, Yan P, Wang Y, et al. Fused angle-polished multi-points side-pumping coupler for monolithic fiber lasers and amplifiers［J］. Optics Communications, 2012, 285(8): 2137-2143.

[53] [53] Larsen J J, Vienne G. Side pumping of double-clad photonic crystal fibers［J］. Optics Letters, 2004, 29(5): 436-438.

[54] [54] Grobelny A, Witkowski J, Beres-Pawlik E. The numerical predictions of the parameters of asymmetrical couplers which pump double-clad lasers［C］. Nottingham: International Conference on Transparent Optical Networks, 2006: 185-188.

[55] [55] Beres-Pawlik E, Grobelny A. Construction of a side pumped double-clad fiber using polished couplers［J］. Optics Communications, 2010, 283(11): 2363-2368.

[56] [56] Jauregui C, Bhme S, Wenetiadis G, et al. Side-pump combiner for all-fiber monolithic fiber lasers and amplifiers［J］. Journal of the Optical Society of America B, 2010, 27(5): 1011-1015.

[57] [57] Polynkin P, Temyanko V, Mansuripur M, et al. Efficient and scalable side pumping scheme for short high-power optical fiber lasers and amplifiers［J］. IEEE Photonics Technology Letters , 2004, 16(9): 2024-2026.

[58] [58] Chen H, Zou S, Yu H, et al. Taper fused fiber bundle 1×4 coupler for high power splitting ［J］. IEEE Photonics Technology Letters, 2015, 27(24): 2527-2530.

[59] [59] Theeg T, Sayinc H, Neumann J, et al. Pump and signal combiner for bi-directional pumping of all-fiber lasers and amplifiers［J］. Optics Express, 2012, 20(27): 28125-28141.

[60] [60] Sayinc H S, Theeg T, Pelegrina-Bonilla G,et al. New pump and signal combiners［C］. Barcelona: Specialty Optical Fibers, 2014: SoW1B.2.

[61] [61] Theeg T, Sayinc H, Neumann J, et al. Side pumping scheme for all-fiber counter-pumping of high power single-frequency fiber amplifiers［C］. Munich: The European Conference on Lasers and Electro-Optics, 2013: CJ_1_2.

[62] [62] Theeg T, Sayinc H, Overmeyer L, et al. Manufacturing and optical characterization of side-pumped high power fiber combiner for LMA-fibers［C］. Munich: The European Conference on Lasers and Electro-Optics, 2015: CE_2_4.

[63] [63] Theeg T, Sayinc H, Neumann J, et al. All-fiber counter-propagation pumped single frequency amplifier stage with 300-W output power［J］. IEEE Photonics Technology Letters, 2012, 24(20): 1864-1867.

[64] [64] Wang Xuejiao, Xiao Qirong, Yan Ping, et al. 3000 W direct-pumping all-fiber laser based on domestically produced fiber［J］. Acta Physica Sinica, 2015, 64(16) : 257-262.

[65] [65] Xiao Q, Yan P, Li D, et al. Bidirectional pumped high power Raman fiber laser［J］. Optics Express, 2016, 24(6): 6758-6768.

[66] [66] Tan Q, Ge T, Zhang X, et al. Cascaded combiners for a high power CW fiber laser［J］. Laser Physics, 2016, 26(2): 025102.

[67] [67] Yan P, Gong M, Li C, et al. Distributed pumping multifiber series fiber laser［J］. Optics Express, 2005, 13(7): 2699-2706.

[68] [68] Chen Xiao, Xiao Qirong, Jin Guangyong, et al. High output power kW class of pump light by (N+1)×1 fiber couplers in a cascaded structure［J］. Acta Photonica Sinica, 2015, 44(6): 28-32.

[69] [69] Grudinin A B, Payne D N, Turner P W, et al. Multi-fibre arrangements for high power fibre lasers and amplifiers: US6826335［P］. 2004-11-30.

[70] [70] Gapontsev V P, Fomin V, Platonov N. Powerful fiber laser system: US7593435［P］. 2009-09-22.

[71] [71] Zhan H, Wang Y, Peng K, et al. 2 kW (2+1) GT-wave fiber amplifier［J］. Laser Physics Letters, 2016, 13(4): 045103.

[72] [72] Zhan H, Wang Y, Peng K, et al. 3.38 kW (3+1) GT-wave fiber［C］. CLEO: Applications and Technology, 2016: ATu3K.7.

[73] [73] Lin Aoxiang， Zhan Huan, Huang Zhihua, et al. 5 kW (N+1) GT-wave fiber ［J］. High Power Laser and Particle Beams, 2016, 28(7): 197-198.

[74] [74] Xiao Q, Ren H, Yan P, et al. Theoretical study of pumping absorption in a co-linear side-pumping coupler［J］. Optics Communications, 2013, 300(14): 220-224.

[75] [75] Xiao Q. Theoretical study of pump absorption of colinear side-pumping coupler with pumping and absorption loops［J］. Optical Engineering, 2013, 52(9): 096111.

[76] [76] Xiao Q, Ren H, Xiao C, et al. Research on characteristics of co-linear side-pumping couplers with special double-clad fibers［J］. Journal of Modern Optics, 2014, 61(4): 307-314.