[1]Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and Key Laboratory of Opto-Electronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China;
[1]Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and Key Laboratory of Opto-Electronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China;
[2]Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, China;
[3]Hebei University of Engineering, Handan 056038, China;
[1]Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and Key Laboratory of Opto-Electronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China;
[1]Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and Key Laboratory of Opto-Electronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China;
[1]Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and Key Laboratory of Opto-Electronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China;
[1]Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and Key Laboratory of Opto-Electronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China;
[1]Center for Terahertz Waves, College of Precision Instrument and Optoelectronics Engineering, and Key Laboratory of Opto-Electronics Information and Technology (Ministry of Education), Tianjin University, Tianjin 300072, China;
[4]School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA;