1. Institute of Photonics and Quantum Electronics (IPQ), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
2. Laboratory of Photonics and Quantum Measurements (LPQM), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
3. Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.