1. Faculty of Physics, "Al. I. Cuza" University, Iasi 700050, Romania
2. Faculty of Electronics and Telecomunications, "Gh. Asachi" Technical University, Iasi 700514, Romania
3. Department of Fluid Mechanics, "Gh. Asachi" Technical University, Iasi 700514, Romania
4. Department of Physics, University of Athens, Athens 15771, Greece
5. Laboratoire de Physique des Lasers, Atomes et Molécules, Centre d’Etudes et de Recherches Lasers et Applications, Université Lille 1 Sciences et Technologies, 59655 Villeneuve d’Ascq Cedex, France
6. Department of Physics, "Gh. Asachi" Technical University, Iasi 700514, Romania