1. Leibniz Institute of Photonic Technology Albert‐Einstein‐Str. 9 07745 Jena Germany
2. Abbe Center of Photonics and Faculty of Physics Friedrich Schiller University Jena Max‐Wien‐Platz 1 07743 Jena Germany
3. Otto Schott Institute of Material Research Friedrich Schiller University Jena Fraunhoferstr. 6 07743 Jena Germany