1. Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, Jena, D-07745, Germany
2. Institute of Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Prague 2, CZ-12116, Czech Republic
3. Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Helmholtzweg 4, Jena, D-07743, Germany