1. Academy for Engineering and Technology Institute for Electric Light Sources Fudan University Shanghai 200433 China
2. College of Mechanical and Automotive Engineering Shanghai University of Engineering Science Shanghai 201620 China
3. College of Electronic and Optical Engineering Nanjing University of Posts and Telecommunications Nanjing 210023 China
4. Department of Microelectronics Delft University of Technology Delft CD 2628 The Netherlands