1. Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Binhai New City, Fuzhou 350207, P. R. China.
2. Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
3. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
4. The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371, Singapore.
5. Institute for Quantum Optics and IQST, Ulm University, Albert-Einstein-Allee 11, Ulm D-89081, Germany.
6. Institute of Materials Research and Engineering, Agency for Science, Technology and Research, Singapore 138634, Singapore.
7. Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore.