1. Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
2. Agency for Science, Technology and Research, Institute of Materials Research and Engineering (IMRE), #08-03, 2 Fusionopolis Way, Innovis 138634, Singapore
3. Key Laboratory of All Optical Network and Advanced Telecommunication Network of Ministry of Education, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
4. Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, United States