1. School of Electrical & Electronic Engineering & The Photonics Institute Nanyang Technological University Singapore 639798 Singapore
2. Singapore Institute of Manufacturing Technology 2 Fusionopolis Way Singapore 138634 Singapore
3. Key Laboratory for Laser Plasmas (Ministry of Education) School of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China
4. School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore