1. School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
2. Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany
3. Carl Zeiss AG, ZEISS Innovation Hub@KIT, Hermann-von-Helmholtz-Platz 6, 76344 Eggenstein-Leopoldshafen, Germany