1. State Key Laboratory on Integrated Optoelectronics; College of Electronic Science and Engineering; Jilin University; 2699 Qianjin Street Changchun 130012 P. R. China
2. School of Chemical and Biomedical Engineering; Nanyang Technological University; 70 Nanyang Drive 637457 Singapore
3. College of Physics; Jilin University; 2699 Qianjin Street Changchun 130012 P. R. China