1. Key Laboratory of High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China.
2. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China.
3. Department of Electrical and Computer Engineering, Boston University, Boston, MA 02215, USA.
4. Photonics Center, Boston University, Boston, MA 02215, USA.
5. Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA.
6. Department of Chemistry, Boston University, Boston, MA 02215, USA.
7. Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47906, USA.