1. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
2. Institute of Biomedical Materials and Devices, Faculty of Science, University of Technology Sydney, Ultimo, New South Wales 2007, Australia.
3. Wigner Research Centre for Physics, Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
4. The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371, Singapore.
5. Department of Atomic Physics, Budapest University of Technology and Economics, Budafokiút 8, H-1111 Budapest, Hungary.