1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
2. Centre for Disruptive Photonic Technologies, The Photonic Institute, 50 Nanyang Avenue, Singapore 639798, Singapore
3. Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore 637616, Singapore
4. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
5. CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Nanyang Technological University, Singapore, 637553, Singapore
6. School of Biomedical Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
7. The University of Sydney Nano Institute, The University of Sydney, Sydney, New South Wales 2006, Australia