Strong-Field-Induced Air Lasing in Nitrogen Glow Discharge PlasmaSupported in part by the National Natural Science Foundation of China (Grant Nos. 61625501 and 62027822), and the Open Fund of the State Key Laboratory of High Field Laser Physics (SIOM).

Abstract

We investigate air lasing at 391 nm, induced by strong laser fields in a nitrogen glow discharge plasma. We generate forward air lasing on the – transition at 391 nm by irradiating an intense 35-fs, 800-nm laser in a pure nitrogen gas, finding that the 391-nm lasing quenches when the nitrogen gas is electrically discharged. In contrast, the 391-nm fluorescence measured from the side of the laser beam is strongly enhanced, demonstrating that this discharge promotes the population in the state. By comparing the lasing and fluorescence spectra of the nitrogen gas obtained in the discharged and laser-induced plasma, we show that the quenching of lasing is caused by the efficient suppression of population inversion between the and states of , in which a much higher population occurs in the state in the discharge plasma. Our results clarify the important role of population inversion in generating air lasing, and also indicate the potential for the enhancement of lasing via further manipulation of the population in the state in the discharged medium.