[1] [1] M. Li, X. Chen, J. Hayashi, and H. Li, Opt. Express 17, 8382 (2009).

[2] [2] J. Bland-Hawthorn, A. Buryak, and K. Kolossovski, J. Opt. Soc. Am. A 25, 153 (2008).

[3] [3] S. Lu, O. Xu, S. Feng, and S. Jian, Chin. Opt. Lett. 7, 469 (2009).

[4] [4] W. H. Loh, F. Q. Zhou, and J. J. Pan, IEEE Photon. Technol. Lett. 11, 1280 (1999).

[5] [5] Y. Nasu and S. Yamashita, J. Lightwave Technol. 23, 1808 (2005).

[6] [6] X. H. Zou, W. Pan, B. Luo, Z. M. Qin, M. Y. Wang, and W. L. Zhang, IEEE Photon. Technol. Lett. 18, 1371 (2006).

[7] [7] J. Aza~na, C. Wang, and L. R. Chen, J. Opt. Soc. Am. B 22, 1829 (2005).

[8] [8] W. H. Loh, F. Q. Zhou, and J. J. Pan, Opt. Lett. 24, 1457 (1999).

[9] [9] J. M. Castro, J. E. Castillo, R. Kostuk, C. M. Greiner, D. Iazikov, T. W. Mossberg, and D. F. Geraghty, IEEE Photon. Technol. Lett. 18, 1615 (2006).

[10] [10] W. Ma, J. Zhou, T. Xu, L. Zhang, and H. Yuan, Chinese J. Laser (in Chinese) 37, 1284 (2010).

[11] [11] C. Wang, J. Aza~na, and L. R. Chen, Opt. Lett. 29, 1590 (2004).

[12] [12] T. Erdogan, J. Lightwave Technol. 15, 1277 (1997).

[13] [13] H. Li, M. Li, and J. Hayashi, Opt. Lett. 34, 938 (2009).

[14] [14] H. Li, Y. Sheng, Y. Li, and J. E. Rothenberg, J. Light-wave Technol. 21, 2074 (2003).