Active medium parameters of molecular nitrogen ions in air laser plasma

In this work, self-seeded lasing pulse duration of the В2Σ+u – X2Σ+g transition of molecular nitrogen ion in air laser plasma at different pump pulse focusing conditions was investigated. Pumping was carried out at the central wavelength of 950 nm, with 60 fs duration (FWHM), and 10 mJ energy. It was shown that lasing pulse duration increases from 1.15 to 4.6 ps, and unsaturated gain coefficient decreases from 6.7 to 4.2 with decreasing pump pulse intensity when geometrical focus length was increased. An explanation for picosecond lasing duration at femtosecond seed amplification is proposed.