1. College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387, China
2. Institute of Information Optics, Zhejiang Normal University, Jinhua, Zhejiang 321004, China
3. Department of Physical Sciences, Dalton State College, Dalton, Georgia 30720, USA
4. Department of Physics and Engineering Physics, The University of Tulsa, Tulsa, Oklahoma 74104, USA