1. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603-146, Beijing 100190, People’s Republic of China
2. Bionanophotonics, Department of Applied Physics, Chalmers University of Technology, Göteborg, SE 41296, Sweden
3. School of Physics and Information Technology, Shaanxi Normal University, 710062 Xi’an, People’s Republic of China
4. Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany