1. State Key Laboratory of Applied Optics, Changchun Institute of Optics; Fine Mechanics & Physics, Chinese Academy of Sciences; No.3888 South Nanhu Road Changchun Jilin P. R. China
2. University of the Chinese Academy of Sciences; Beijing 10039 P.R. China
3. Department of Applied Physics; Hong Kong Polytechnic University; Hung Hom Kowloon Hong Kong
4. School of Physical Electronics; University of Electronic Science and Technology of China; Chengdu 610054 Sichuan Province China