1. Nanophotonics and Ultrafine Optoelectronic System, Beijing Key Laboratory, School of Physics, Beijing Institute of Technology, 5 South Street of Zhongguancun, 100081 Beijing, China
2. Department of Applied Physics, KTH-Royal Institute of Technology, Electrum 229, 16440 Kista, Sweden
3. School of Materials Science & Engineering, Beijing Institute of Technology, 5 South Street of Zhongguancun, 100081 Beijing, China
4. Henan Key Lab of Information-based Electrical Appliances, School of Electrical and Information Engineering, Zhengzhou University of Light Industry, 450002 Zhengzhou, China