1. The Key Laboratory
of Weak Light Nonlinear Photonics, Ministry of Education, School of
Physics and TEDA Institute of Applied Physics, Nankai University, Tianjin 300071, China
2. Beijing National
Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China
3. Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States