1. Centre for Disruptive Photonic Technologies TPI Nanyang Technological University 637371 Singapore
2. School of Physical and Mathematical Sciences Nanyang Technological University 637371 Singapore
3. RMIT University Department of Physics School of Applied Sciences Melbourne VIC 3000 Australia
4. Centre for OptoElectronics and Biophotonics School of Electrical and Electronic Engineering Nanyang Technological University 639798 Singapore
5. Optoelectronics Research Centre and Centre for Photonic Metamaterials University of Southampton SO17 1BJ UK