1. Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig-Maximilians-Universität München, Munich, Germany
2. Department of Chemistry and CeNS, Ludwig-Maximilians-Universität München, Munich, Germany
3. Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, United States
4. Department of Physical Chemistry, Technische Universität Dresden, Dresden, Germany