1. Microsystem and Terahertz Research Center, China Academy of Engineering Physics, Chengdu 610200, P. R. China
2. Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang 621999, P. R. China
3. Nano Science and Technology Institute, University of Science and Technology of China, Hefei 230062, P. R. China
4. National Space Science Center, Chinese Academy of Sciences, Beijing 100190, P. R. China
5. Beijing Computational Science Research Center, Beijing 100193, P. R. China