1. Istituto di Cibernetica 'E.Caianiello', Consiglio Nazionale delle Ricerche, Via Campi Flegrei, 34, 80078, Pozzuoli, Italy
2. Instituto de Nanociencia de Aragon, University of Zaragoza. C/ Mariano Esquillor s/n, Zaragoza, Spain
3. Philipps University of Marburg, FB Physics, Biophotonics, Renthof 7, D-35037 Marburg, Germany