1. Nonlinear Physics Centre Australian National University Canberra ACT 2601 Australia
2. Center for Terahertz Waves Tianjin University Tianjin 300072 China
3. Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore
4. Centre for Disruptive Photonic Technologies The Photonics Institute Nanyang Technological University Singapore 639798 Singapore
5. Department of Nanophotonics and Metamaterials ITMO University St Petersburg 197101 Russia
6. Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak Ridge TN 37831 USA