1. Department of Physics, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
2. Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstr. 2, 12489 Berlin, Germany
3. Leibniz-Institute for Crystal Growth, Max-Born-Str. 2, 12489 Berlin, Germany
4. Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany
5. Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20740, USA
6. Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, Nizhny Novgorod, 603950, Russia
7. Nizhny Novgorod State University, 23 Prospekt Gargarina, Nizhny Novgorod 603950, Russia