1. Department of Mathematics and Physics, Università Cattolica del Sacro Cuore, Brescia I-25133, Italy
2. ILAMP (Interdisciplinary Laboratories for Advanced Materials Physics), Università Cattolica del Sacro Cuore, Brescia I-25133, Italy
3. Department of Physics and Astronomy, KU Leuven, B-3001 Leuven, Belgium
4. Italian Institute of Technology (IIT), Genova 16163, Italy
5. CNR-INO (National Institute of Optics), via Branze 45, 25123 Brescia, Italy
6. Department of Information Engineering, University of Brescia, Brescia I-25123, Italy
7. IFN-CNR, Piazza Leonardo da Vinci 32, I-20133, Milano, Italy
8. Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano, Italy
9. Division of Chemical Physics, Department of Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden