1. State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai 200050, China
2. School of Physics, University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing, 100049, China
3. National Laboratory for Infrared Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083, China
4. Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg, Sweden