1. The Guo Photonics LaboratoryState Key Laboratory of Applied OpticsChangchun Institute of Optics, Fine Mechanics and PhysicsChinese Academy of Sciences Changchun 130033 P. R. China
2. Department of Materials Science and Optoelectronics EngineeringUniversity of Chinese Academy of Sciences Beijing 100049 P. R. China
3. School of PhysicsFaculty of ScienceUniversity of Sydney Sydney NSW 2006 Australia
4. The Institute of OpticsUniversity of Rochester Rochester NY 14627 USA