1. School of Life Science, Shandong Normal University, Jinan 250014, P. R. China
2. Shandong Key Laboratory of Biophysics, Institute of Biophysics, College of Physics and Electronic Information, Dezhou University, Dezhou 253023, P. R. China
3. Institute of Crystal Materials, Advanced Research Center for Optics, Shandong University, Jinan 250100, P. R. China