1. Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany
2. Abbe Center of Photonics and Faculty of Physics, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
3. Chair in Hybrid Nanosystems, Nanoinstitute Munich, Ludwig-Maximilians-Universität Munich, Königinstrasse 10, 80539 Munich, Germany
4. 4th Physics Institute and Research Center SCoPE, University of Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany
5. The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom
6. Otto Schott Institute of Materials Research (OSIM), Friedrich-Schiller-Universität Jena, Fraunhoferstr. 6, 07743 Jena, Germany