1. State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, 500 Yu Tian Road, Shanghai200083, P. R. China
2. University of Chinese Academy of Sciences, 19 Yu Quan Road, Beijing100049, P. R. China
3. Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 1 Sub-Lane Xiangshan, Hangzhou310024, P. R. China
4. School of Science, Xihua University, 9999 Hongguang Avenue, Chengdu610039, P.R. China
5. Institute of Optoelectronics, Fudan University, 2005 Songhu Road, Shanghai200438, P. R. China