1. National Institute for Laser, Plasma and Radiation Physics (INFLPR), Ilfov, 077125 Magurele, Romania
2. Faculty of Physics, University of Bucharest, Ilfov, 077125 Magurele, Romania
3. Faculty of Applied Chemistry and Materials Science, University Politehnica Bucharest, 313 Spl. Independentei, 060042 Bucharest, Romania
4. National Institute R&D for Optoelectronics, INOE 2000, 409 Atomistilor Str, Ilfov, 077125 Magurele, Romania