1. College of Physics and Optoelectronic EngineeringShenzhen University Shenzhen 518060 P. R. China
2. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong ProvinceCollege of Physics and Optoelectronic EngineeringShenzhen University Shenzhen 518060 P. R. China
3. State Key Lab of Advanced Displays and Optoelectronics TechnologiesThe Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong
4. School of Electronic and Information EngineeringSouth China University of Technology Guangzhou 510640 P. R. China