1. Key Laboratory of Optoelectronic Technology & Systems (Ministry of Education), College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, China
2. Microsystem and Terahertz Research Center, China Academy of Engineering Physics, Chengdu 610200, China
3. Insititute of Electronic Engineering, China Academy of Engineering Physics, Mianyang 621900, China