1. Institute of Microelectronics Agency for Science, Technology and Research 2 Fusionopolis Way Singapore 138634 Singapore
2. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore 637371 Singapore
3. Center for Disruptive Photonic Technologies The Photonics Institute, Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore