1. Key Laboratory of Excited State Physics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, and Graduate School of Chinese Academy of Sciences, 16 Eastern Nan-Hu Road, Changchun 130033, P. R. China, and State Key Laboratory of Integral Optoelectronics, College of Electronic Science and Engineering, JiLin University, Changchun 130012, P. R. China