1. L. Chen, M. X. Liao and J. W. Xiong, Journal of Optoelectronics Laser 19, 278 (2008). (in Chinese)
2. W. Tian, F. Wu, W. J. Chen and G. L. Zhang, Journal of Optoelectronics Laser 20, 342 (2009). (in Chinese)
3. J. J. Zheng, G. L. Zhang and X. S. Zhang, Journal of Optoelectronics Laser 18, 443 (2007). (in Chinese)
4. Z. Y. Ren, H. Yang, L. C. Shen and S. D. Han, J. Mater. Sci.-Mater. Electron. 19, 1 (2008).
5. J. F. Suyver, S. F. Wuister, J. J. Kelly and A. Meijerink, Nano Lett. 1, 429 (2001).