1. Key Laboratory of Optoelectronic Technology & Systems (Chongqing University), Ministry of Education , and College of Optoelectronic Engineering, Chongqing University , Chongqing 400044 , China
2. State Key Lab of Optical Technologies on Nano-fabrication and Micro-engineering , Institute of Optics and Electronics, Chinese Academy of Sciences , Chengdu 610209 , China