1. Department of Chemistry, National University of Singapore, Singapore 117543, Singapore
2. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological UniversityRINGGOLD, Singapore 637371, Singapore
3. The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 639798, Singapore
4. Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
5. Institute of Materials Research and Engineering, Agency for Science, Technology and Research, Singapore 138634, Singapore