Effect of rotational wave packets on the stimulated emission of nitrogen with light filament

Abstract

We measure forward emission of the nitrogen ion excited by light filaments at 800 nm. The radiation strongly depends on light polarization and orbital angular momentum. In all cases the rotational distribution of nitrogen molecules plays an essential role in the 428 nm stimulated emission.

Transient gain from N2+ in light filaments

“…The shift in the wavepacket distribution in B and X state suggests that the two states have different interaction with ultrashort pulses. Both distributions are shifted to higher rotational numbers than a thermal distribution [18], with X state occupying the highest rotational numbers. By comparing the Fourier amplitude of B and X in lower rotational states one might conclude that the B state has a higher population that the X state, hence the stimulated emission would be governed by a traditional population inversion.…”

“…4, ω e = 2419.84, ν ′′ = 0, ω e X e = 23. 18, ω e Y e = -0.537, α e = 0.024, B e = 2.07456, D e = 6.17 • 10 −6 for the B state [9]. B ν is calculated as B ν = B e − α e (ν + 1 2 ).…”

Recent Advances in Air Lasing: A Perspective from Quantum Coherence

“…Molecular nitrogen ion (N) lasing is the third type of air lasing, which originates from the transition from the excited state to the ground state . Lasing actions from N ions have been experimentally observed by several research groups since the first report in 2011 . Besides its promising application in the remote sensing similar to the other two types of air lasing, the understanding of the physical procedure in N lasing is also attracting great interests.…”

“…Lasing actions from N + 2 ions have been experimentally observed by several research groups since the first report in 2011. [22,25,[27][28][29][30][66][67][68][69][70][71][72][73][74][75][76][77] Besides its promising application in the remote sensing similar to the other two types of air lasing, the understanding of the physical procedure in N + 2 lasing is also attracting great interests. Moreover, the generation of N + 2 lasing is the result of a complex interaction between strong laser fields and nitrogen molecules.…”

Terahertz control of air lasing

“…Such reports have reinforced the idea that a lasing process is at the origin of the coherent emission. However, the mechanism responsible for the gain is still not fully understood, although it is likely that laser-driven couplings between electronic states in the ion [13,14], and rotational effects [15][16][17][18][19][20][21] play a role.…”