1. Beijing Center for Crystal Research and Development, Key Lab of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, P. R. China
3. Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900, P. R. China
4. Department of Physics, Tamkang University, Tamsui, New Tapei 25137, Taiwan