1. Key Laboratory of Advanced Micro/Nano Electronic Devices & Smart Systems of ZhejiangCollege of Information Science and Electronic EngineeringZhejiang University Hangzhou 310027 China
2. Department of PhysicsMassachusetts Institute of Technology Cambridge MA 02139 USA
3. Division of Physics and Applied PhysicsSchool of Physical and Mathematical SciencesNanyang Technological University 21 Nanyang Link Singapore 637371 Singapore
4. State Key Laboratory of Integrated OptoelectronicsCollege of Electronic Science and EngineeringJilin University 2699 Qianjin Street Changchun 130012 China
5. School of Information Science and EngineeringShandong University Qingdao 266237 China