1. Department of Physics and Astronomy, University of Canterbury, PB 4800, Christchurch 8140, New Zealand
2. Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russia
3. MacDiarmid Institute for Advanced Materials and Nanotechnology, P.O. Box 600, Wellington 6140, New Zealand
4. Dodd-Walls Centre for Photonic and Quantum Technologies and Department of Physics and Astronomy, University of Canterbury, PB4800, Christchurch 8140, New Zealand
5. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia