Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering;
Key Laboratory of Optoelectronic Information Technology;
Ministry of Education;
Tianjin University;
300072 Tianjin;
China;
Department of Electrical and Electronic Engineering;
Southern University of Science and Technology;
518055 Shenzhen;
China;
School of Electrical and Computer Engineering;
Oklahoma State University;
Stillwater;
OK 74078;
USA;