1. Laboratory of Ultrafast Spectroscopy and the Lausanne Centre for Ultrafast Science, ISIC, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
2. National Research Council of Italy – Institute of Photonics and Nanotechnologies (CNR-IFN), via Trasea 7, 35131 Padova, Italy