1. Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert Einstein Str. 6, 07745 Jena, Germany
2. The Netherlands Organization for Applied Scientific Research, TNO, 2628CK Delft, The Netherlands
3. RHK Technology, Troy, Michigan 48083, USA
4. Fraunhofer Institute for Applied Optics and Precision Engineering, Albert Einstein Str. 7, 07745 Jena, Germany