1. Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, United Kingdom
2. Laser Zentrum Hannover e.V., D-30419 Hannover, Germany
3. CNRS-CRHEA, Université Côte d’Azur, 06560 Valbonne, France
4. Institute of Quantum Matter, Ulm University, D-89081 Ulm, Germany
5. Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield S1 3JD, United Kingdom