1. Institute of Solid State Physics, Technische Universität Berlin, Berlin, Germany
2. 4th Physics Institute and Research Center SCoPE and Integrated Quantum Science and Technology Center IQST, University of Stuttgart, Stuttgart, Germany
3. Institute for Applied Optics (ITO) and Research Center SCoPE, University of Stuttgart, Stuttgart, Germany
4. Institut für Halbleiteroptik und Funktionelle Grenzflächen, Center for Integrated Quantum Science and Technology (IQST) and Research Center SCoPE, University of Stuttgart, Stuttgart, Germany