1. School of Information Sciences and Engineering Shandong University Qingdao 266237 P. R. China
2. Key Laboratory of Laser & Infrared System (Shandong University) Ministry of Education Shandong University Qingdao 266237 P. R. China
3. Department of Applied Physics Photonics Research Institute The Hong Kong Polytechnic University Hong Kong P. R. China
4. Key Laboratory of Energy Conversion and Storage Technologies (Southern University of Science and Technology) Ministry of Education Shenzhen 518055 P. R. China