[1] CNRS, UMR 5209, ICB, Grp Opt Champ Proche, F-21078 Dijon, France
[2] Commissariat Energie Atom, Dept Rech Fondamentale Matiere Condensee, Lab SiNaPS MINATEC, F-38054 Grenoble 9, France
[3] CNRS, Lab Charles Fabry Inst Opt, F-91403 Orsay, France
[4] CNRS, Lab Technol Microelect, F-38054 Grenoble 9, France