[1] Y. Li, B. Yao, Z. Wang, Y. Wang, and Y. Ju, Chin. Opt. Lett. 4, 470 (2006).

[2] B. Yao, L. Dong, Y. Wang, Y. Ju, X. Yu, W. Sun, and Y. Li, Acta Opt. Sin. (in Chinese) 24, 79 (2004).

[3] Y. Li, B. Yao, and Y. Wang, Chin. Opt. Lett. 4, 175 (2006).

[4] Y. Wang, W. He, B. Yao, and Y. Ju, Chinese J. Lasers (in Chinese) 33, 730 (2006).

[5] B. Yao, X. Zhang, Y. Wang, W. He, Y. Li, and Y. Ju, Chin. Opt. Lett. 2, 595 (2004).

[6] G. J. Koch, J. P. Deyst, and M. E. Storm, Opt. Lett. 18, 1235 (1993).

[7] J. D. Kmetec, T. S. Kubo, T. J. Kane, and C. J. Grund, Opt. Lett. 19, 186 (1994).

[8] N. P. Barnes, M. G. Jani, and R. L. Hutcheson, Appl. Opt. 34, 4290 (1995).

[9] V. Wulfmeyer, M. Randall, A. Brewer, and R. M. Hardesty, Opt. Lett. 25, 1228 (2000).

[10] K. Scholle, E. Heumann, and G. Huber, Laser Phys. Lett. 1, 285 (2004).