1. Institute of Applied PhysicsAbbe Center of PhotonicsFriedrich‐Schiller‐Universität Jena 07743 Jena Germany
2. Leibniz Institute of Photonic Technology 07702 Jena Germany
3. Fraunhofer Institute for Applied Optics and Precision Engineering 07745 Jena Germany
4. Institute of Theoretical Solid State PhysicsKarlsruhe Institute of Technology 76131 Karlsruhe Germany
5. Institute of NanotechnologyKarlsruhe Institute of Technology 76021 Karlsruhe Germany