[1] Y. Kunio, Y. Hidetsugu, K. Yoshiaki. IEEE J. Quantum Electron., 24, 1118(1988).
[2] Z. Zhao, B. Jiang, Y. Zhang, Y. Liu, X. Xu, P. Song, X. Wang, J. Xu. Chin. Opt. Lett., 3, 163(2005).
[3] C. Zuo, J. Hou, B. Zhang, J. He. Chin. Opt. Lett., 13, 021401(2015).
[4] X. Fu, Z. Jia, Y. Li, D. Yuan, C. Dong, X. Tao. Opt. Mater. Express, 2, 1242(2012).
[5] B. Cockayne, D. Gasson, D. Findlay, D. Goodwin, R. Clay. J. Phys. Chem. Solids, 29, 905(1968).
[12] Y. Li, J. Li, X. Liu, J. Wu, X. Zhang. Laser Phys., 22, 531(2012).
[13] B. Aull, H. Jenssen. IEEE J. Quantum Electron., 18, 925(1982).
[15] Y. Chang, Y. Huang, K. Su, Y. Chen. Opt. Express, 16, 21155(2008).