[1] T. F. Krauss, Phys. Stat. Sol. (a) 197, 688 (2003).

[2] S. Balslev, B. Bilenberg, D. Nilsson, A. M. Jorgensen, A. Kristensen, O. Geschke, J. P. Kutter, K. B. Mogensen, and D. Snakenborg, Proc. SPIE 5730, 211 (2005).

[3] L. Eldada and L. W. Shacklette, IEEE J. Sel. Topics Quant. Electron. 6, 54 (2000).

[4] W. Ni, X.Wu, and J.Wu, Opt. Express. 17, 1194 (2009).

[5] H. Lin, J. Su, R. Cheng, and W. Wang, IEEE J. Quantum Electron. 35, 1092 (1999).

[6] C. Huang, C. Chang, and W. Wang, Microwave Opt. Technol. Lett. 38, 337 (2003).

[7] J. Zhou, H. Shen, H. Zhang, and X. Liu, Chin. Opt. Lett. 7, 1041 (2009).

[8] Y. Gao, Z. Gong, R. Bai, Y. Hao, X. Li, X. Jiang, M. Wang, J. Pan, and J. Yang, Chin. Phys. Lett. 25, 2912 (2008).

[9] A. K. Das, Appl. Opt. 42, 1236 (2003).

[10] M. Olivero, M. Svalgaard, L. Jocou, and J. Berger, J. Lightwave Technol. 25, 367 (2007).

[11] K. F rch and M. Svalgaard, IEEE Photon. Technol. Lett. 14, 173 (2002).

[12] C. Peucheret, Y. Geng, M. Svalgaard, B. Zsigri, H. R. S rensen, N. Chi, H. Deyerl, M. Kristensen, and P. Jeppesen, IEEE Photon. Technol. Lett. 17, 1674 (2005).

[13] M. Svalgaard, K. F rch, and L. Andersen, IEEE Photon. Technol. Lett. 21, 2097 (2003).

[14] S. Li, Q. Lin, W. Ni, X. Lou, and X. Wu, Acta Opt. Sin. (in Chinese) 28, 1062 (2008).