1. College of Electronic Science and TechnologyShenzhen University Shenzhen 518060 P. R. China
2. State Key Lab of Advanced Displays and Optoelectronics TechnologiesHong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong
3. Department of Electronic and Computer EngineeringThe 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