1. Hubei Key Laboratory of Optical Information and Pattern Recognition Wuhan Institute of Technology Wuhan Hubei 430205 P. R. China
2. School of Electronics and Information Engineering Hubei University of Science and Technology Xianning 437100 P. R. China
3. School of Optoelectronic Information and Energy Engineering Wuhan Institute of Technology Wuhan Hubei 430205 P. R. China
4. School of Chemical Engineering & Pharmacy Wuhan Institute of Technology Wuhan Hubei 430205 P. R. China
5. School of Physics and Technology, Key Laboratory of Artificial Micro- and Nano-structures of the Ministry of Education and School of Physics and Technology Wuhan University Wuhan 430072 P. R. China