1. Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, 07745 Jena, Germany
2. Center for Materials Research, Norfolk State University, Norfolk, Virginia 23504, United States
3. Nonlinear Physics Centre, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 2601, Australia
4. Institute of Theoretical Solid State Physics, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
5. Institute of Nanotechnology, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
6. Laser Physics Centre, Research School of Physics and Engineering, The Australian National University, Canberra, ACT 2601, Australia