1. Microsystem and Terahertz Research Center China Academy of Engineering Physics 596 Yin He Road, Shuangliu Chengdu 610200 China
2. Institute of Electronic Engineering China Academy of Engineering Physics 64 Mianshan Road, Youxian Mianyang 621999 China
3. College of Physics Sichuan University Wuhou Chengdu 610065 China