1. Mines Saint-Etienne, University of Lyon, CNRS, UMR 5307 LGF, Centre SMS, F-42023 Saint-Etienne, France
2. University of Lyon, UJM-St-Etienne, CNRS, Institute of Optics Graduate School, Laboratoire Hubert Curien UMR 5516, F-42023 Saint-Etienne, France
3. Arizona Center for Mathematical Sciences and College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
4. GIE Manutech-USD, 42000 Saint-Etienne, France