[1
]Institute of Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster,
Germany
[2
]Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT),
Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
[3
]Humboldt-Universität zu Berlin, Institut für Physik, AG Theoretische Optik & Photonik,
Newtonstr. 15, 12489 Berlin, Germany
[4
]Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany
[5
]Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), 76021 Karlsruhe,
Germany
[6
]Institute of Applied Physics, Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe,
Germany