Affiliation: | a CNR-Istituto di Acustica ‘O.M. Corbino', Via Cassia, 1216, I-00189 Rome, Italy b Laser Department, INFPLR, P.O. Box MG-16, RO-76900 Bucharest, Romania c PASTIS-CNRSM, 72100 Brindisi, Italy d INFM, P.O. Box MG-16, RO-76900 Bucharest, Romania |