1. Key Laboratory for Microstructural Material Physics of Hebei Province, School of Science, Yanshan University, Qinhuangdao, Hebei 066004, P. R. China
2. Laboratory for Biomedical Photonics, Institute of Laser Engineering, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, P. R. China
3. Department of Physics, Zhejiang Sci-Tech University, Hangzhou, Zhejiang 310018, P. R. China