1. Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Helmholtzweg 4, D-07743 Jena, Germany
2. Leibniz Institute of Photonic Technology, Albert-Einstein Str. 9, 07745 Jena, Germany
3. Institut für Festkörperphysik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
4. Research Center for Applied Sciences, Academia Sinica, 128 Sec. 2, Academia Road, Nankang District, Taipei 11529, Taiwan
5. Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan