Air lasing: Phenomena and mechanisms<xref rid="cpb_28_11_114204fn1" ref-type="fn">*</xref><fn id="cpb_28_11_114204fn1"><label>*</label><p>Project supported by the National Natural Science Foundation of China (Grant Nos. 61625501, 61427816, and 11904121), the Open Fund of the State Key Laboratory of High Field Laser Physics (SIOM), China, the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT), China (Grant No. 2017TD-21), and Fundamental Research Funds for the Central Universities of China.</p></fn>

Air lasing: Phenomena and mechanisms**

Project supported by the National Natural Science Foundation of China (Grant Nos. 61625501, 61427816, and 11904121), the Open Fund of the State Key Laboratory of High Field Laser Physics (SIOM), China, the Program for JLU Science and Technology Innovative Research Team (JLUSTIRT), China (Grant No. 2017TD-21), and Fundamental Research Funds for the Central Universities of China.

Li Helong^{1, 2}, Yao Danwen², Wang Siqi², Fu Yao², Xu Huailiang^{2, 3, †}

(a) Schematics of the ionization and coupling concept for the population inversion in N2+ , (b) forward spectrum of air lasing induced by a few-cycle laser pulse, and (c) numerical simulation of time-dependent populations in the three electronic states, in which the few-cycle laser field (grey curve) is presented for comparison.^[85]