2025/04/25 by Wenli Yang, Ping Li, Yang, Wenli +10
Engineering · Physics and Astronomy · #Geophysics and Sensor Technology #Quantum optics and atomic interactions #Mechanical and Optical Resonators
paper · pdf · doi:10.48550/arxiv.2504.18124
N2+ air lasing has attracted considerable attention due to its promising applications in remote sensing and the debates surrounding its generation mechanisms. Here, we present a comprehensive theoretical investigation of the role of molecular rotation in N2+ lasing at 391 nm (B2 Σu+(v''=0)→ X2 Σg+ (v=0)). By solving the open-system density matrix and Maxwell-Bloch equations in a rovibronic-state basis, we examine both the formation of the N2+ gain medium induced by a femtosecond pump pulse and the subsequent spatial propagation of the seed pulse. During the pump stage, rotational dynamics are found to significantly modify the angle-dependent populations of ionic vibrational-electronic states within tens of femtoseconds. Furthermore, ionization-produced rotational coherences substantially enhance the population inversion between the X2 Σg+ (v=0) and B2 Σu+(v''=0) states. In the seed propagation stage, both population inversion and rotational coherence are found to contribute to the lasing process, with the latter playing a dominant role in amplifying the lasing signals. These findings reveal the crucial role of molecular rotation in N2+ air lasing and highlight its potential as a tunable parameter for controlling lasing dynamics.