[1] T. Y. Fan and R. L. Byer, Opt. Lett. 12, 809 (1987).
[2] Y. Chen, H. Peng, W. Hou, Q. Peng, A. Geng, L. Guo, D. Cui, and Z. Xu, Appl. Phys. B 83, 241 (2006).
[3] W. Liu, Y. Huo, and S. He, Acta Opt. Sin. (in Chinese) 22, 980 (2002).
[4] H. Zhang, X. Meng, L. Zhu, J. Liu, C. Wang, and Z. Shao, Opt. Laser Technol. 31, 279 (1999).
[5] C. Wang, Y. Chow, L. Reekie, W. Gambling, H. Zhang, L. Zhu, and X. Meng, Appl. Phys. B 70, 769 (2000).
[6] F. Jia, Q. Xue, Q. Zheng, Y. Bu, and L. Qian, Appl. Phys. B 83, 245 (2006).