1. Institute of Applied Physics,
Abbe Center of Photonics, Friedrich Schiller University Jena, Max-Wien-Platz 1, 07743 Jena, Germany
2. Max Planck Institute for the Science of Light, 91058 Erlangen, Germany
3. Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany
4. Solid State Electronics Department
and CeNIDE, University of Duisburg-Essen, Lotharstr. 55, 47048 Duisburg, Germany
5. Fraunhofer Institute of Applied Optics and Precision Engineering, Albert-Einstein-Str.
7, 07745 Jena, Germany