1. Key Laboratory of Advanced Transducers and Intelligent Control System, Ministry of Education and Shanxi Province, Taiyuan University of Technology, No. 79, Yingze West Main Street, Taiyuan 030024, P. R. China
2. College of Physics and Optoelectronics, Taiyuan University of Technology, No. 79, Yingze West Main Street, Taiyuan 030024, P. R. China