We investigate N_(2)^(+) air lasing at 391 nm,induced by strong laser fields in a nitrogen glow discharge plasma.We generate forward N_(2)^(+) air lasing on the B^(2)Σ_(u)^(+)(v’=0)-X^(2)Σ_(g)^(+)(v"=0) transi...We investigate N_(2)^(+) air lasing at 391 nm,induced by strong laser fields in a nitrogen glow discharge plasma.We generate forward N_(2)^(+) air lasing on the B^(2)Σ_(u)^(+)(v’=0)-X^(2)Σ_(g)^(+)(v"=0) 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 B^(2)Σ_(u)^(+)(v’=0) 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 N_(2)^(+) lasing is caused by the efficient suppression of population inversion between the B^(2)Σ_(u)^(+) and X^(2)Σ_(g)^(+) states of N_(2)^(+),in which a much higher population occurs in the X^(2)Σ_(g)^(+) state in the discharge plasma.Our results clarify the important role of population inversion in generating N_(2)^(+) air lasing,and also indicate the potential for the enhancement of N_(2)^(+) lasing via further manipulation of the population in the X^(2)Σ_(g)^(+) state in the discharged medium.展开更多
基金the National Natural Science Foundation of China(Grant Nos.61625501 and 62027822)the Open Fund of the State Key Laboratory of High Field Laser Physics(SIOM)。
文摘We investigate N_(2)^(+) air lasing at 391 nm,induced by strong laser fields in a nitrogen glow discharge plasma.We generate forward N_(2)^(+) air lasing on the B^(2)Σ_(u)^(+)(v’=0)-X^(2)Σ_(g)^(+)(v"=0) 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 B^(2)Σ_(u)^(+)(v’=0) 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 N_(2)^(+) lasing is caused by the efficient suppression of population inversion between the B^(2)Σ_(u)^(+) and X^(2)Σ_(g)^(+) states of N_(2)^(+),in which a much higher population occurs in the X^(2)Σ_(g)^(+) state in the discharge plasma.Our results clarify the important role of population inversion in generating N_(2)^(+) air lasing,and also indicate the potential for the enhancement of N_(2)^(+) lasing via further manipulation of the population in the X^(2)Σ_(g)^(+) state in the discharged medium.
