1. School of Optical and Electronic Information, Optics Valley Laboratory, Huazhong University of Science and Technology, 1037 Luoyu Road, Hongshan District, Wuhan 430074, P.R. China
2. Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
3. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. Shenzhen Huazhong University of Science and Technology Research Institute, Shenzhen, Guangdong 518057, P.R. China
5. Department of Physical Science and Technology, School of Science, Wuhan University of Technology, 205 Luoshi Road, Wuhan 430070, P.R. China