1. State Key Laboratory on Integrated Optoelectronics; College of Electronic Science and Engineering; Jilin University; 2699 Qianjin Street Changchun 130012 P. R. China
2. State Key Laboratory of Robotics; Shenyang Institute of Automation; Chinese Academy of Sciences; Shenyang 110016 P. R. China
3. College of Physics; Jilin University; 119 Jiefang Road Changchun 130023 P. R. China