Optimization of N2+ lasing through population depletion in the X2Σg+

Coherent N2 + emission mediated by coherent Raman scattering for gas-phase thermometry

“…In the present work, we report on air lasing mediated by CRS, whereby a filament is generated by an fs near-IR pump pulse, and the coherent N 2 + emission at 428 nm is seeded by a narrowband picosecond (ps) probe pulse, via non-resonant (NR) CRS of the latter. The seeding mechanism observed here is clearly different from that of similar experiments, where the coherent emission results from self-seeding [20,21] or by the use of twocolor collinear pump-probe schemes employing fs seed pulses, spectrally broad enough to cover the fluorescence wavelength [11,22,23]. We employ a single regenerative amplifier system (7.5 mJ, 1 kHz, Astrella Coherent) to generate the fs pump and the ps probe pulses.…”

Control of N2+ air lasing

“…Elliptical [11] and polarization-modulated [7,13,14] pump pulses exploit the postionization interaction with the A 2 u state to control gain, but these experiments are complicated because the pump pulse acts before, during, and after ionization. A second weak excitation pulse can reduce ambiguity because it acts only on the ion independent of ionization.…”

Modeling of the processes of ionization and excitation of nitrogen molecules by short and intense laser pulses

“…Dipole moments for the considered states depend on the vibrational quantum number. This fact was not accounted for in previous publications [5,12,29], which leads to quantitative differences in the populations of excited levels.…”

“…Some authors [5,7,29,30] have proposed to associate ionization with the maximum of the laser pulse and then to solve the amplitude equations for the second half of the pulse for the evaluation of population at the excited levels. However, our analysis shows that such a scheme is inconsistent with the density matrix approach showing quantitatively different results for the ionization level and populations at excited states.…”