1. School of Science and Engineering The Chinese University of Hong Kong Shenzhen 518172 P. R. China
2. Department of Electrical and Electronic Engineering Southern University of Science and Technology Shenzhen 518055 P. R. China
3. State Key Laboratory of High Power Semiconductor Laser School of Science Changchun University of Science and Technology Changchun 130022 P. R. China
4. Core Research Facilities Southern University of Science and Technology Shenzhen 518055 P. R. China
5. College of New Materials and New Energies Shenzhen Technology University Shenzhen 518118 P. R. China