[1] [1] P Russell. Photonic crystal fibers[J]. Science, 2003, 299(5605): 358-362.

[2] [2] N A Mortensen. Effective area of photonic crystal fibers[J]. Opt Express, 2002, 10(7): 341-348.

[3] [3] J Limpert, T Schreiber, A Liem, et al.. High-power air-clad large-mode-area photonic crystal fiber laser[J]. Opt Express, 2003, 11(7): 818-823.

[4] [4] Zhou Dechun, Yu Fengxia, Lu Jingjuan, et al.. Design of Yb-doped all-fiber laser device based on optical fiber gratings resonator[J]. Acta Photonia Sinica, 2010, 39(3): 389-392.

[5] [5] J Limpert, T Schreiber, A Liem, et al.. Thermo-optical properties of air-clad photonic crystal fiber lasers in high power operation[J]. Opt Express, 2003, 11（22）: 2982-2990.

[6] [6] Yu Chongxiu, Yuan Jinhui, Shen Xiangwei. Recent progress of study on photonic crystal fiber[J]. Acta Optica Sinica, 2011, 31(9): 0900139

[7] [7] Zhang Guang, Zhou Qinling, Hu Lili, et al.. A large core phosphate photonic crystal fiber made by a stack-and-draw technique[J]. Chinese J Lasers, 2011, 38(1): 0106003.

[8] [8] Lou Qihong, Zhou Jun, Zhang Haibo, et al.. Recent progress of large core fiber lasers[J]. Chinese J Lasers, 2010, 37(9): 2235-2241.

[9] [9] J W Dawson, M J Messerly, R J Beach, et al.. Analysis of the scalability of diffraction-limited fiber lasers and amplifiers to high average power[J]. Opt Express, 2008, 16(17): 13240-13266.

[10] [10] M Aslund, J Canning, S D Jackson, et al.. Diffraction in air-clad fibres[J]. Opt Express, 2005, 13(14): 5227-5233.

[11] [11] F Stutzki, F Jansen, C Jauregui, et al.. Non-hexagonal large-pitch fibers for enhanced mode discrimination[J]. Opt Express, 2011, 19(13): 12081-12086.

[12] [12] N A Mortensen, J R Folkenberg, M D Nielsen, et al.. Modal cut off and the V-parameter in photonic crystal fibers[J]. Opt Lett, 2003, 28(20): 1879-1881.

[13] [13] S G Yang, Y J Zhang, X Z Peng, et al.. Theoretical study and experimental fabrication of high negative dispersion photonic crystal fiber with large area mode field[J]. Opt Express, 2006, 14(7): 3015-3023.