1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371
2. Centre for Disruptive Photonic Technologies, The Photonic Institute, 50 Nanyang Avenue, Singapore 639798
3. The Institute of Optics, University of Rochester, 275 Hutchison Road, Rochester, New York 14620, United States
4. Department of Physics, Case Western Reserve University, 10600 Euclid Avenue, Cleveland, Ohio 44106, United States
5. Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore 637616
6. CNR-NANOTEC and Department of Physics, University of Calabria, 87036 Rende, Italy