1. Laboratory of Photonic Materials and Fibre Devices (FIMAP) Institute of Materials École Polytechnique Fédérale de Lausanne Lausanne 1015 Switzerland
2. Empa Swiss Federal Laboratories for Materials Science and Technology Center for X‐Ray Analytics St. Gallen CH‐9014 Switzerland
3. ARTORG Center for Biomedical Engineering Research University of Bern Murtenstrasse 50 Bern 3008 Switzerland
4. Department of Chemistry University of Fribourg Chemin du Musée 9 Fribourg 1700 Switzerland