Key Laboratory of Optoelectronic Information Acquisition & Manipulation of Ministry of Education of China School of Physics & Material Science Anhui University Hefei 230039 China;
Department of Physics Shaoguan University Shaoguan 512005 China;
Key Laboratory of Optoelectronic Information Acquisition & Manipulation of Ministry of Education of China School of Physics & Material Science Anhui University Hefei 230039 China;
Key Laboratory of Optoelectronic Information Acquisition & Manipulation of Ministry of Education of China School of Physics & Material Science Anhui University Hefei 230039 China;