1. School of Physics and Electronic Engineering, Jiangsu University, Zhenjiang 212013, China
2. College of Information Science and Technology, Nanjing Forestry University, Nanjing 210037, China
3. School of Physics and Materials Science, Nanchang University, Nanchang 330031, China
4. Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117542, Singapore