1 Laboratory of Solid-State Quantum Electronics, National Institute for Laser, Plasma and Radiation Physics, Bucharest R-077125, Romania 2 Solid-State Laser Laboratory, Laser Department, National Institute for Laser, Plasma and Radiation Physics, Bucharest R-077125, Romania 3 University of Bucharest, Doctoral School of Physics, Romania Corresponding author: Nicolaie PAVEL, E-mail: nicolaie.pave...