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.
Theoretical and experimental study of nonresonance generation of laser radiation by atoms, molecules and ions of matter - superradiation - is an important area of research in the field of femtosecond optics. Narrowly directed (forward and reverse), with an intensity proportional to the square of the number of inverted atoms, molecules and ions, radiation can be used to probe the atmosphere using femtosecond lidars. This paper presents the results of comparative experimental studies of the appearance of superradiance at transitions of molecular nitrogen ion in the atmosphere and at transitions of atomic strontium ion in a mixture with inert gases (He, Ne) in a heated cuvette. For the first time, superradiance was observed in the transition from the resonant electronic state 2Р1/2 / to the ground state 2S1/2 (407.8 nm), when Sr pairs were pumped by radiation at a wavelength of 268.1 nm.
THz generation experimental results in a filament plasma produced by focusing ultrashort Ti:Sapphire laser pulses at a wavelength of 950 nm are reported. A study of structure and time-resolved dynamics of forming the laser filament is carried out. THz radiation dependence from filament length and pump energy is also given. Optimal conditions for efficient THz generating were found.
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