1. Nonlinear Physics Centre, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 2601 Australia
2. Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, 07745 Jena, Germany
3. School of Engineering and Information Technology, University of New South Wales, Canberra, ACT 2600, Australia
4. Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 2601, Australia
5. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950, Russia
6. Photonics Laboratory, Physics Unit, Tampere University, P.O. Box 692, FI-33014 Tampere, Finland