1. Key Laboratory of Digital Medical Engineering of Hebei Province, College of Electron and Information Engineering, Hebei University, Baoding 071002, People's Republic of China
2. Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore 117576
3. College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
4. Key Laboratory of Optoelectronic Information and Sensing Technologies of Guangdong Higher Education Institutes, Jinan University, Guangzhou 510632, China