1. Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
2. China Tianchen Engineering Corporation, Tianjin 300400, China
3. Shanghai Key Lab of Modern Optical System, University of Shanghai for Science and Technology, Shanghai 200093, China
4. State Key Laboratory on Integrated Optoelectronics and College of Electronic Science and Engineering, Jilin University, Changchun 130012, China