1. Micro- and Nanophotonic Materials Group, Research Institute for Materials Science and Engineering, University of Mons, 20 Place du Parc, Mons B-7000, Belgium
2. Materia Nova, Avenue N. Copernic 3, Mons B-7000, Belgium
3. Univ. Lille, ENSAIT, ULR 2461 - GEMTEX - Génie et Matériaux Textiles, F-59000 Lille, France
4. Junia, F-59000 Lille, France