1. Nanophotonics and Metrology Laboratory, École Polytechnique Fédéral de Lausanne, Station 11, 1015 Lausanne, Switzerland, Laboratory of Metal Physics and Technology, Swiss Federal Institute of Technology Zürich, CH-8093 Zürich, Switzerland, LASMEA, UMR 6602 CNRS, Université Blaise Pascal, 24, av des Landais, 63177 Aubière, France, and A. M. Prokhorov General Physics Institute RAS, Vavilova 38, Moscow 119991, Russia