1. Material Science and Engineering; King Abdullah University of Science & Technology (KAUST); Thuwal 23955-6900 Saudi Arabia
2. Division of Nanophotonics; CAS Key Laboratory of Standardization and Measurement for Nanotechnology; CAS Center for Excellence in Nanoscience; National Center for Nanoscience and Technology; Beijing 100190 P. R. China
3. Department of Physics; The University of Hong Kong; Pokfulam Road Hong Kong 999077 China
4. School of Materials Science and Engineering; University of New South Wales (UNSW); Sydney NSW 2052 Australia