[2] [2] Wang Li, Yang Jingwei, Cai Xuwu, et al.. 2.09 μm nanosecond holmium laser pumped ZnGeP2 optical parametric oscillator[J]. Chinese J Lasers, 2014, 41(1): 0102008.

[3] [3] Lü Tao, Zhang Wei, Chen Fang. Experimental research of dissecting biological soft tissues induced by fiber-guided Q-switched thulium:YAG laser microsurgical scalpel[J]. Acta Optica Sinica, 2014, 34(11): 1117001.

[4] [4] Scholle K, Lamrini S, Koopmann P, et al.. 2 μm laser sources and their possible applications[M].//Bishnu Pal. Frontiers in Guided Wave Optics and Optoelectronics. Rijeka: INTECH, 2010: 471-500.

[5] [5] Geng J, Wang Q, Jiang S. 2 μm fiber laser sources and their applications[C]. SPIE, 2011, 8164: 816409.

[6] [6] Walsh B M. Review of Tm and Ho materials: Spectroscopy and lasers[J]. Laser Physics, 2009, 19(4): 855-866.

[7] [7] Oh K , Morse T F, Kilian A, et al.. Continuous-wave oscillation of thulium-sensitized holmium-doped silica fiber laser[J]. Optics Letters, 1994, 19(4): 278-280.

[8] [8] Jackson S D, Mossman S. High-power diode-cladding-pumped Tm3+, Ho3+-doped silica fibre laser[J]. Applied Physics B, 2003, 77(5): 489-491.

[9] [9] Yuen T, Billy R, David B, et al.. Tm3+/Ho3+ codoped tellurite fiber laser[J]. Optics Letters, 2008, 33(11): 1282-1284.

[10] [10] Xue G, Zhang B, Yin K, et al.. All-fiber wavelength-tunable Tm/Ho-codoped laser between 1727 nm and 2030 nm[C]. SPIE, 2015, 9255: 92550U.

[11] [11] Min B, Yoon H, Lee W, et al.. Performance improvement of wideband EDFA by ASE injection from C band to L band amplifier[C]. Proceedings of the Fifth Asia-Pacific Conference on Communications and Fourth Optoelectronics and Communications Conference, 1999, (2): 1346-1347.

[12] [12] Hui Xiaoli, Lin Rujian. Gain enhanced L-band erbium-doped fiber amplifier using a single fiber Bragg grating[J]. Optical Communication Technology, 2003, 27(10): 31-33.

[13] [13] Harun S W, Subramaniam T, Tamchek N, et al.. Gain and noise figure performances of L-band EDFA with an injection of C-band ASE[J]. Jurnal Teknologi, 2004, 40(D): 9-16.

[14] [14] Han Q, Yao Y, Chen Y, et al.. Highly efficient Er/Yb-codoped fiber amplifier with an Yb-band fiber Bragg grating[J]. Optics Letters, 2015, 40(11): 2634-2636.

[15] [15] Gao G, Wang G, Yu C, et al.. Investigation of 2.0 μm emission in Tm3+ and Ho3+ co-doped oxyfluoride tellurite glass[J]. Journal of Luminescence, 2009, 129(9): 1042-1047.

[16] [16] Jackson S D, King T A. CW operation of a 1.064-μm pumped Tm-Ho-doped silica fiber laser[J]. IEEE Journal of Quantum Electronics, 1998, 34(9): 1578-1587.

[17] [17] Allain J Y, Monerie M, Poignant H. High-efficiency CW thulium-sensitised holmium-doped fluoride fibre laser operating at 2.04 μm[J]. Electronics Letters, 1991, 27(17): 1513-1515.

[18] [18] Feng T, Yan F, Peng W, et al.. Theoretical analysis of characteristics for 2 μm Tm3+∶Ho3+ co-doped silica fiber laser pumped by a 1550 nm fiber laser[J]. Optical Fiber Technology, 2012, 18(4): 204-208.

[19] [19] Digonnet M J, Gaeta C J. Theoretical analysis of optical fiber laser amplifiers and oscillators[J]. Applied Optics, 1985, 24(3): 333-342.

[20] [20] Mao Q, Wang J, Sun X, et al.. A theoretical analysis of amplification characteristics of bi-directional erbium-doped fiber amplifiers with single erbium-doped fiber[J]. Optics Communications, 1999, 159(1-3): 149-157.

[21] [21] Zou X, Toratani H. Spectroscopic properties and energy transfers in Tm3+ singly and Tm3+ Ho3+ doubly-doped glasses[J]. Journal of Non-Crystalline Solids, 1996, 195(1-2): 113-124.

[22] [22] Wang J. Theoretical modelling of thulium-sensitized holmium continuous-wave fibre lasers[J]. Journal of Modern Optics, 2007, 41(7): 1457-1472.