1. National Research Council (CNR)-; National Institute of Optics (INO); Largo Enrico Fermi 6 50125 Florence Italy
2. Department of Physics and Astronomy; University of Florence; National Institute of Nuclear Physics (INFN); Via Sansone 1 50019 Sesto Fiorentino (FI) Italy
3. Institute of Information Theory and Automation; Czech Academy of Science; Pod Vodárenskou věží 4 18208 Prague Czech Republic
4. Private practice; formerly Opificio delle Pietre Dure di Firenze; Italy