1. Department of Electrical and Computer Engineering University of California Los Angeles CA 90095 USA
2. School of Material Science and Engineering Harbin Institute of Technology Shenzhen Guangdong 518055 China
3. Department of Electronic and Computer Engineering Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China
4. Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China
5. Fibertek Inc. Herndon VA 20171 USA
6. US Army Research Laboratory Adelphi MD 20783 USA
7. US Army Research Laboratory Playa Vista CA 90094 USA
8. Department of Electrical and Computer Engineering Department of Physics and Astronomy and Department of Materials Science and Engineering University of California Los Angeles CA 90095 USA