1 Centre for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Zijingang Campus, Hangzhou 310058, China
2 State Key Laboratory of Advanced Optical Communication Systems and Networks, Department of Electronic Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
3 Institute for Energy Efficiency, University of California Santa Barbara, Santa Barbara, California 93106, USA
4 Electrical and Computer Engineering Department, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
5 Wuhan National Laboratory for Optoelectronics & School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
6 National Information Optoelectronics Innovation Center, China Information and Communication Technologies Group Corporation (CICT), Wuhan 430074, China
7 State Key Laboratory of Optical Communication Technologies and Networks, China Information and Communication Technologies Group Corporation (CICT), Wuhan 430074, China
8 Department of Electronic Engineering, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China