1. Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications Institute of Photonics Technology Jinan University Guangzhou 510632 P. R. China
2. Department of Materials Science and Engineering Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 P. R. China
3. Photonics Initiative Advanced Science Research Center City University of New York 85 St. Nicholas Terrace New York NY 10031 USA
4. Physics Program The Graduate Center City University of New York 365 Fifth Avenue New York NY 10016 USA
5. Department of Electrical Engineering City College of New York New York NY 10031 USA