1. Centre for Disruptive
Photonic Technologies, Nanyang Technological University, Singapore, 637371
2. Department of Electrical
and Computer Engineering, National University of Singapore, Singapore, 117576
3. Institute of Materials Research and Engineering, Agency for Science,
Technology and Research (A*STAR), 3 Research Link, Singapore, 117602
4. Optoelectronics
Research Centre and Centre for Photonic Metamaterials, University of Southampton, Southampton SO17 1BJ, United Kingdom