1. Key Laboratory of Optoelectronic Technology and Systems (Chongqing University) Ministry of Education School of Optoelectronic Engineering Chongqing University 174 Shazheng Street, Shapingba Chongqing 400044 China
2. Key Laboratory of Terahertz Solid State Technology Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences 865 Changning Road Shanghai 200050 China