1. School of Optoelectronic Engineering, Guangxi Key Laboratory of Optoelectronic Information Processing, Guilin University of Electronic Technology, Guilin 541004, People’s Republic of China
2. School of Materials Science and Engineering, Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Technology, Guilin 541004, People’s Republic of China
3. Shanghai Applied Radiation Institute, Shanghai University, No. 20, Chengzhong Road, Shanghai 200444, China
4. Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and Key Laboratory of Optoelectronics Information and Technology, Ministry of Education of China, Tianjin 300072, China