[1] Univ Paris 11, CNRS, Photophys Mol Lab, F-91405 Orsay, France
[2] CNRS, F-31055 Toulouse, France
[3] Univ Bourgogne, CNRS, UMR 5209, Inst Carnot Bourgogne, F-21078 Dijon, France
[4] Swiss Fed Inst Technol Lausanne EPFL, Nanophoton & Metrol Lab, CH-1015 Lausanne, Switzerland