1. Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117576, Singapore
2. Institute of Laser Engineering, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, China
3. Key Laboratory of Trans-Scale Laser Manufacturing Technology of Ministry of Education, Beijing 100124, China
4. School of Aerospace Engineering, Xiamen University, Xiamen 361005, China