1. Institute for Advanced Materials and Technology University of Science and Technology Beijing 100083 China
2. Department of Materials Science and Engineering and Centre for Functional Photonics (CFP) City University of Hong Kong Kowloon Hong Kong S.A.R.
3. Department of Chemical Physics and NanoLund Lund University P. O. Box 124 22100 Lund Sweden
4. B. I. Stepanov Institute of Physics National Academy of Sciences of Belarus 68 Nezaležnasci Ave., 220072 Minsk Belarus