[1] D. Chen and L. Shen, J. Lightwave Technol. 25, 2700 (2007).
[2] D. Chen and L. Shen, IEEE Photon. Technol. Lett. 19, 185 (2007).
[3] F. Beltran-Mejia, G. Chesini, E. Silvestre, A. K. George, J. C. Knight, and C. M. B. Cordeiro, Opt. Lett. 35, 544 ( 2010).
[4] K. Saitoh, M. Koshiba, T. Hasegawa, and E. Sasaoka, Opt. Express 11, 843 (2004).
[5] A. Huttunen and P. T¨orm¨a, Opt. Express 13, 627 (2005).
[6] S. Yang, Y. Zhang, X. Peng, Y. Lu, S. Xie, J. Li, W. Chen, Z. Jiang, J. Peng, and H. Li, Opt. Express 14, 3015 (2006).
[7] L. Han, L. Liu, Z. Yu, H. Zhao, X. Song, J. Mu, X. Wu, L. Long, and X. Liu, Chin. Opt. Lett. 12, 010603 (2014).
[8] J. C. Knight and D. V. Skryabin, Opt. Express 15, 15365 (2007).
[9] T. A. Briks, J. C. Knight, and P. St. J. Russel, Opt. Lett. 22, 961 (1997).
[10] Z. Lian, P. Horak. X. Feng, L. Xiao, K. Frampton, N. White, J. A. Tucknott, H. Rutt, D. N. Payne, W. Stewart, and W. H. Loh, Opt. Express 20, 29386 (2012).
[11] D. Chen, G. Hu, and L. Chen, IEEE Photon. Technol. Lett. 23, 1851 (2011).
[12] Y. Shen, G. Yu, J. Fu, and L. Zou, Chin. Opt. Lett. 10, 021301 (2012).
[13] M. Szpulak, T. Martynkien, and W. Urbanczyk, Appl. Opt. 43, 4739 (2004).
[14] C. Wu, B. Guan, Z. Wang, and X. Feng, J. Lightwave Technol. 28, 1392 (2010).
[15] W. Huang, J. Opt. Soc. Am. A 11, 963 (1994).
[16] H. Xie, P. Dabkiewicz, R. Ulrich, and K. Okamoto, Opt. Lett. 11, 333 (1986).
[17] M. N. Charasse, M. Turpin, and J. P. Le Pesant, Opt. Lett. 16, 1043 (1991).