Theory of femtosecond strong field ion excitation and subsequent lasing in N.sup.+./sup..sub.2./sub.

0548945 - FZÚ 2022 RIV GB eng J - Journal Article
Tikhonchuk, Vladimir - Liu, Y. - Danylo, R. - Houard, A. - Mysyrowicz, A.
Theory of femtosecond strong field ion excitation and subsequent lasing in N⁺₂.
New Journal of Physics. Roč. 23, č. 2 (2021), č. článku 023035. ISSN 1367-2630. E-ISSN 1367-2630
R&D Projects: GA MŠMT LQ1606
Research Infrastructure: ELI Beamlines III - 90141
Institutional support: RVO:68378271
Keywords : lasing * ion excitation * femtosecond laser
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 3.716, year: 2021
Method of publishing: Open access

Delayed cavity-free forward lasing at the wavelengths of 391 and 428 nm was observed in recent experiments in air or pure nitrogen pumped with an intense femtosecond laser pulse at wavelength of 800 nm. The mechanism responsible for the lasing is highly controversial. In this article we propose a model explaining the delayed lasing, which contains two parts: (i) ionization of neutral nitrogen molecules and subsequent excitation of nitrogen ions in a strong pump laser pulse, and (ii) coherent emission of excited ions due to the presence of long-lived polarizations maintained by a weak laser post-pulse and coupling simultaneously ground state X2Σ+g to states A2Πu and B2Σ+u of singly ionized nitrogen molecules N+2 . Two regimes of signal amplification are identified: a signal of a few picosecond duration at low gas pressures and a short (sub-picosecond) signal at high gas pressures. The theoretical model compares favorably with results obtained by different
Permanent Link: http://hdl.handle.net/11104/0325001