1. Institute of Applied Physics and Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Straße 15, 07745 Jena, Germany
2. Center of Excellence in Photonics, Fraunhofer Institute for Applied Optics and Precision Engineering IOF, Albert-Einstein-Straße 7, 07745 Jena, Germany
3. Institute of Solid-State Physics, Friedrich Schiller University Jena, Helmholtzweg 5, 07743 Jena, Germany
4. Institute of Materials Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany