1. State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 P. R. China
2. School of Physical Science and Technology Shanghaitech University Shanghai 201210 P. R. China
3. Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
4. Centre for Optical and Electromagnetic Research and International Research Center for Advanced Photonics College of Optical Science and Engineering Zhejiang University Hangzhou 310058 P. R. China