1. Microsystem and Terahertz Research Center, China Academy of Engineering Physics, Chengdu, 610299, China
2. Department of Physics, Sichuan University, Sichuan, 610065, China
3. School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, China
4. Institute of Electronic Engineering, China Academy of Engineering Physics, 64 Mianshan Road, Youxian, Mianyang 621999, China