1. Department of Electrical and Computer Engineering and Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
2. Key Laboratory of Luminescence and Optical Information, Beijing Jiaotong University, Ministry of Education, Beijing 100044, China
3. Institute of Optoelectronics Technology, Beijing Jiaotong University, Beijing 100044, China
4. Ottawa IC Laboratory, Huawei Canada, 19 Allstate Parkway, Markham, Ontario L3R 5B4, Canada
5. Ipswich Research Centre, Huawei Technologies Research & Development (UK) Ltd., Phoenix House, (B55), Adastral Park, Ipswich IP5 3RE, U.K.