1. Terahertz Science Cooperative Innovation Center, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, China
2. National Key Laboratory of Application Specific Integrated Circuit, Hebei Semiconductor Research Institute, Shijiazhuang, China
3. Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI, USA
4. Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, China