1. Key Laboratory of Optoelectronic Technology & Systems, Ministry of Education, Chongqing University, Chongqing, P. R. China
2. Key Laboratory of Fundamental Science of Micro/Nano-Device and System Technology, Chongqing University, Chongqing, P. R. China
3. International R & D center of Micro-nano Systems and New Materials Technology, College of Optoelectronic Engineering, Chongqing University, Chongqing, P. R. China