1. Wuhan National Laboratory for Optoelectronics, Wenzhou Advanced Manufacturing Technology Research Institute, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
2. School of Physics and Telecommunications, Huanggang Normal University, Huangzhou 438000, P. R. China
3. Department of Physics, University of Yangon, Kamaryut, Yangon 11041, Myanmar
4. Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Environment and Materials, Guangxi Institute Fullerene Technology, Guangxi University, Nanning 530004, P. R. China