1. Department of Electronic EngineeringEast China Normal University 500 Dongchuan Road Shanghai 200241 China
2. Shanghai Institute of Intelligent Electronics & SystemsFudan University 220 Handan Road Shanghai 200433 China
3. Department of Electronic EngineeringOptoelectronics Engineering Research CenterXiamen University 422 Siming South Road Xiamen 361005 China
4. Institute for Solid State PhysicsThe University of Tokyo 5‐1‐5 Kashiwanoha Kashiwa Chiba 277–8581 Japan
5. Suzhou Institute of Nano‐tech and Nano‐bionicsChinese Academy of Sciences Suzhou 215123 China