1. Center for Terahertz waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University and the Key Laboratory of Optoelectronics Information and Technology (Ministry of Education), Tianjin 300072, China
2. State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084, China
3. Research Center for Intelligent Chips and Devices, Zhejiang Lab, Hangzhou 311121, China
4. School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
5. Guangxi Key Laboratory of Optoelectronic Information Processing, School of Optoelectronic Engineering, Guilin University of Electronic Technology, Guilin 541004, P. R. China