1. Centre for Disruptive Photonic Technologies TPI Nanyang Technological University 21 Nanyang Link Singapore 637371 Singapore
2. Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore 637371 Singapore
3. Institute of Materials Research and Engineering Agency for Science, Technology and Research (A*STAR) 2 Fusionopolis Way Singapore 138634 Singapore