[1] Y. X. Bai, N. L. Wu, J. Zhang, J. Q. Li, S. Q. Li, J. Xu, and P. Z. Deng, Appl. Opt. 36, 2468 (1997).
[2] U. Keller, Nonlinear Optics in Semiconductors II, Semiconductors and Semimetals (Academic Press, New York, 1999) pp. 211-285.
[3] L. Fulop, L. Fulbert, and E. Molva, in Proceedings of Conference on Lasers and Electro-Optics 1998 136 (1998).
[4] J. Song, C. Li, N. S. Kim, and K. Ueda, Appl. Opt. 39, 4954 (2000).
[5] Y. F. Chen, S. W. Tsai, and S. C. Wang, Opt. Lett. 25, 1442 (2000).
[6] Y. F. Chen and Y. P. Lan, Appl. Phys. B 74, 415 (2002).
[7] C. Li, J. Song, D. Shen, N. S. Kim, J. Lu, and K. Ueda, Appl. Phys. B 70, 471 (2000).
[8] A. Agnesi and S. Dell'acqua, Appl. Phys. B 76, 351 (2003).
