1. Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, United States
2. Key Laboratory of Optoelectronics Information Technology, Ministry of Education, Tianjin University, Tianjin 300072, China
3. School of Optical and Electronic Information and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China
4. Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
5. Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, United States