[1] [1] P. Jiang, D. Yang, Y. Wang, T. Chen, B. Wu, and Y. Shen, Laser Phys. Lett. 6, 384 (2009).

[2] [2] C. Ye, P. Yan, M. Gong, and M. Lei, Chin. Opt. Lett. 3, 249 (2005).

[3] [3] M. D. Mermelstein, in Proceedings of Optical Amplif iers and Their Applications/Coherent Optical Technologies and Applications OMC2 (2006).

[4] [4] X. Huang, B. Guo, W. Yang, G. Chen, X. Gong, Y. Kong, D. Li, X. Li, Z. Sui, M. Li, and J. Wang, Chin. Opt. Lett. 7, 712 (2009).

[5] [5] Y. Kong, Q. Liu, C. Deng, F. Tian, and X. Huang, J. Modern Opt. 56, 597 (2009).

[6] [6] W. Cheng, H. Zhang, M. Liu, C. Zheng, P. Yan, and M. Gong, J. Opt. 13, 085204 (2011).

[7] [7] P. Wan, J. Liu, L. Yang, and F. Amzajerdian, Opt. Express 19, 18067 (2011).

[8] [8] H. Kalaycioglu, K. Eken, and F. O Ilday, Opt. Lett. 36, 3383 (2011).

[9] [9] C. Zheng, H. Zhang, P. Yan, and M. Gong, Opt. Laser Technol. 49, 284 (2013).

[10] [10] T. Wei, J. Li, and J. Zhu, Chin. Opt. Lett. 10, 040605 (2012).

[11] [11] W. Zhang, J. Ning, and B. Chen, Adv. Mater. Res. 403, 2508 (2012).

[12] [12] W. Yong and P. Hong, J. Lightwave Technol. 21, 2262 (2003).

[13] [13] R. LeVeque, Finite Dif ference Methods for Ordinary and Partial Dif ferential Equations: Steady-State and Timedependent Problems (Society for Industrial and Applied Mathematics, Philadelphia, 2007).

[14] [14] R. Paschotta, J. Nilsson, A. C. Tropper, and D. C. Hanna, IEEE J. Quantum Electron. 33, 1049 (1997).

[15] [15] O. Svelto, Principles of lasers (Springer, Berlin, 2009).

[16] [16] J. Boullet, R. Dubrasquet, C. Medina, R. Bello-Doua, N. Traynor, and E. Cormier, Opt. Lett. 35, 1650 (2010).