1. Faculty of Physics and CeNS Ludwig‐Maximilians‐Universität Geschwister‐Scholl‐Platz 1 80539 München Germany
2. Institute of Physical Chemistry and Abbe Center of Photonics Friedrich Schiller University Jena Lessingstr. 10 07743 Jena Germany
3. Faculty of Physics Nanospectroscopy Group and Center for NanoScience Nano‐Institute Munich Ludwig‐Maximilians‐Universität München Königinstr. 10 80539 Munich Germany
4. Leibniz Institute of Photonic Technology (IPHT) Albert‐Einstein‐Str. 9 07745 Jena Germany