1. National Laboratory for Infrared Physics,
Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
2. Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
3. University of Chinese Academy of Sciences, Beijing 100049, China
4. Department
of Physics and Key Laboratory of Artificial Micro- and Nano-Structures
of Ministry of Education, Wuhan University, Wuhan 430072, China
5. Key Laboratory of Polar Materials and Devices
of MOE, East China Normal University, Shanghai 200241, China
6. Key Laboratory for Micro-Nano Physics and
Technology of Hunan Province, Key Laboratory for Micro/Nano Optoelectronic
Devices of Ministry of Education, College of Physics and Microelectronics, Hunan University, Changsha 410082, China