Abstract
We investigate lasing of a nitrogen gas induced by intense femtosecond laser pulses at around 400 nm. By examining both the self-induced and externally seeded forward emission spectra, we unambiguously identify the lasing actions at 427.8 and 423.6 nm assigned respectively to the (0, 1) and (1, 2) emissions and show that the lasing mechanism is totally different from the lasing induced by near-infrared (800 nm) laser pulses, in which the population transfer from to proceeds through the resonant transition, facilitating the population inversion between the states [Phys. Rev. Lett. 123, 203201 (2019)]. We simulate the population distributions among the vibrational levels in the three lowest electronic states of by the 400-nm laser pumping and find that the population is efficiently transferred between the state and the state by a Rabi oscillation combined with a Raman-type transition, leading to the population inversion so that the lasing occurs at the (0, 1) and (1, 2) emissions.
- Received 4 July 2021
- Accepted 24 August 2021
DOI:https://doi.org/10.1103/PhysRevA.104.032823
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