[1] TRAVERS J C, RULKCY A B, CUMBERLAND B A, et al.. Visible supercontinuum generation in photonic crystal fibers with a 400 W continuous wave fiber laser ［J］. Optics Express, 2008, 16(19): 14435-14447.

[2] WAN P, YANG L M, LIU J. High pulse energy 2 μm femtosecond fiber laser ［J］. Optics Express, 2013, 21(2): 1798-1803.

[3] ANDREW S R, KADWANI P, LAWRENCE SHAH A S, et al.. 1 μJ, sub-500 fs chirped pulse amplification in a Tm-doped fiber system ［J］. Optics Letters, 2013, 38(2): 121-123.

[4] FAUCHER M, LIZE Y K. Mode field adaptation for high power fiber lasers ［C］.Conference on Lasers and Electro-Optics, Optical Society of America, 2007: CFI7.

[5] HOU J, CHEN SH P, CHEN Z L, et al.. Recent developments and key technology analysis of high power supercontinuum source ［J］. Laser & Optoelectronics Progress, 2013, 50(080010): 1-13. (in Chinese)

[6] DONG F L, ZHAO F ZH, GE T W, et al.. Optimization of beam quality for all-fiber lasers ［J］. Opt. Precision Eng., 2014, 22(4): 844-849. (in Chinese)

[7] GAO J, YU F, KUANG H SH, et al.. Generation of supercontinuum spectra from acousto-optic Q-switched nanosecond fiber lasers ［J］. Opt. Precision Eng., 2014, 22(5): 1138-1142. (in Chinese).

[8] HOFMANN P, MAFI A, JOLLIVET C, et al.. Detailed investigation of mode-field adapters utilizing multimode-interference in graded index fibers ［J］. Journal of Lightwave Technology, 2012, 30(14): 2289-2298.

[9] KERTTULA J, FILIPPOV V, USTIMCHIK V, et al.. Mode evolution in long tapered fibers with high tapering ratio ［J］. Optics Express, 2012, 20(23): 25461-25470.

[10] HU X, ZHANG W P, YIN R G, et al.. Coupling efficiency and transmission mode of laser beam in tapered multimode fiber ［J］. Infrared and Laser Engineering, 2013, 42(2): 372-375. (in Chinese)

[11] ZHOU X, CHEN Z, ZHOU H, et al.. Mode-field adaptor between large-mode-area fiber and single-mode fiber based on fiber tapering and thermally expanded core technique ［J］. Applied Optics, 2014, 53(22): 5053-5057.

[12] ZHOU X, CHEN Z, CHEN H, et al.. Mode field adaptation between single-mode fiber and large mode area fiber by thermally expanded core technique ［J］. Optics & Laser Technology, 2013, 47: 72-75.

[13] SHIRAISHI K, YANAGI T, KAWAKAMI S. Light-propagation characteristics in thermally diffused expanded core fibers ［J］. Journal of Lightwave Technology, 1993, 11(10): 1584-1591.

[14] RATUSZEK M. Analysis of loss of single mode telecommunication fiber thermally diffused core areas ［C］. Lightguides and Their Applications III. International Society for Optics and Photonics, 2007: 660817-660817-6.