1. Key Laboratory of Optoelectronic Technology & Systems, Ministry of Education of China, College of Optoelectronic Engineering, Chongqing University, 400044 Chongqing, P. R. China
2. Chongqing Key Laboratory of Multi-scale Manufacturing Technology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, 400714 Chongqing, P. R. China
3. Institut für Physik, Carl von Ossietzky Universität, D-26111 Oldenburg, Germany