1. Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China
2. National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu-tian Road, Shanghai 200083, China
3. Department of Physics, Shanghai Normal University, 100 Gui Lin Road, Shanghai 200234, China
4. School of Information Science and Engineering, Fudan University, 220 Handan Road, Shanghai 200433, China