**Author details**

Wenqing Liu, Zhenyi Chen\* , Pinhua Xie, Jianguo Liu and Tianshu Zhang

\*Address all correspondence to: zychen@aiofm.ac.cn

State Environmental Protection Key Laboratory of Optical Monitoring Technology, Ministry of Environmental Protection of the People's Republic of China, Anhui Institute of Optics & Fine Mechanics, Chinese Academy of Sciences, Hefei, Anhui, P.R. China
