Vibrational and electronic excitation of ionized nitrogen molecules in intense laser fields

Zhong, Xunqi; Miao, Zhiming; Zhang, Linlin; Liang, Qi; Lei, Mingwei; Jiang, Hongbing; Liu, Yunquan; Gong, Qihuang; Wu, Chengyin

doi:10.1103/physreva.96.043422

Cited by 44 publications

(32 citation statements)

References 30 publications

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“…of gain is related to the decay of rotational wave packets. While this long-term gain is similar to gain reported in air and using a gas cell [4,6,10,[21][22][23][24], we also measure unusual short-term gain that exists within a few hundred femtoseconds of the pump pulse. To highlight the complex effects that cause the modulations in gain, we present simulations of the modulations obtained by propagating the probe pulse through the evolving rotationally excited and inverted medium.…”

Section: Introductionsupporting

confidence: 79%

Short- and long-term gain dynamics in N2+ air lasing

et al. 2019

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Air lasing in the nitrogen molecular ion is not well understood because the complex physics responsible for gain is interwoven with pulse propagation in an extreme environment. Here we use a short gas jet to limit the interaction length, thereby removing the propagation effects. We report on several mechanisms that contribute to the decay of gain in different conditions, and experimentally isolate two decay timescales: the decay of long-term gain due to collisional state mixing, and short-term gain that cannot be explained by population inversion. To test the former, we control the inelastic electron scattering rate by varying the gas concentration while keeping the propagation length fixed, and predict the change of the decay using a model of collisional state mixing. We show that the same mechanism causes the decay of rotational wave packets in the states of the ion. Finally, we simulate the complex modulations of gain due to rotational wave packets and the propagation of the probe pulse through the evolving rotationally excited and inverted medium.

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Section: Introductionsupporting

confidence: 79%

Short- and long-term gain dynamics in N2+ air lasing

et al. 2019

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“…Thus, the amplified emission can emerge without any delay after the probe, in contrast to the experimentally observed delays of ∼1 to 8 ps between the probe pulse and the enhanced 391 nm emission reported in Refs. [14,22,24,31,35,37]. This retardation has been attributed to the effect of probe-triggered superradiance [22,24,31,37], whereas the origin of the optical amplification is still debated.…”

Section: Resultsmentioning

confidence: 99%

“…Most experiments studying the amplification effect around the 391 nm line in N + 2 are done in a pump-probe scenario [14,[20][21][22]24,26,27,[30][31][32][34][35][36][37][38][39][41][42][43][44]: an intense pump pulse prepares the gas, and the transient absorption (or gain) of a delayed probe pulse is measured. The theoretical results presented below focus on this scenario, with the pump pulse carried at 800 nm.…”

Section: Theoretical Frameworkmentioning

confidence: 99%

Rotational Quantum Beat Lasing without Inversion

Richter

Lytova

Morales

et al. 2020

OSA High-Brightness Sources and Light-Driven Interactions Congress 2020 (EUVXRAY, HILAS, MICS)

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In standard lasers, light amplification requires population inversion between an upper and a lower state to break the reciprocity between absorption and stimulated emission. However, in a medium prepared in a specific superposition state, quantum interference may fully suppress absorption while leaving stimulated emission intact, opening the possibility of lasing without inversion. Here we show that lasing without inversion arises naturally during propagation of intense femtosecond laser pulses in air. It is triggered by the combination of molecular ionization and molecular alignment, both unavoidable in intense light fields. The effect could enable inversionless amplification of broadband radiation in many molecular gases, opening unusual opportunities for remote sensing.Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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“…Based on the fact that a picosecond‐delayed external seed is significantly amplified for both the co‐propagation and counter‐propagation cases of the pump and seed pulses, this kind of lasing action is attributed to the seed amplification in N

_{2}^{+}

ions with the population inversion . Some scenarios have been proposed to explain its ultrafast gain, including the collisional excitation of rescattering electrons, multiple‐states couplings, the alignment‐induced transient inversion, etc. For details of this specific subject, one can refer to a recent review .…”

Section: Molecular Nitrogen Ion Lasingmentioning

confidence: 99%

“…Therefore, the process of the N

_{2}^{+}

lasing spans over different timescales and hence provides a versatile platform for investigating molecular dynamics, ultrafast nonlinear phenomena, and quantum optics in the system of molecular ions . On the other hand, the understanding of the gain mechanism in N

_{2}^{+}

lasing is highly desired in the strong‐field‐ionization framework, which has motivated many tentative and interesting explanations . Up to now, it is still lack of a complete physical picture to explain all key experimental observations on N

_{2}^{+}

lasing.…”

Section: Molecular Nitrogen Ion Lasingmentioning

confidence: 99%

Recent Advances in Air Lasing: A Perspective from Quantum Coherence

et al. 2019

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The research topic of air lasing is of fundamental and practical importance, which has grown rapidly in the past decade. Air lasing, or a laser‐like emission from air species including atomic oxygen, atomic argon, atomic nitrogen, molecular nitrogen, and molecular nitrogen ions, has been investigated vastly in both experiment and theory. In this review, the basic concepts of air lasing are discussed and the crucial role of quantum coherence in the air‐lasing process is highlighted. As an exciting perspective, air lasing not only exhibits important fundamental physics such as superradiance, nonlinear effects, vibrational and rotational dynamics, but also shows potential practical implications toward remote sensing.

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Vibrational and electronic excitation of ionized nitrogen molecules in intense laser fields

Cited by 44 publications

References 30 publications

Short- and long-term gain dynamics in N2+ air lasing

Short- and long-term gain dynamics in N2+ air lasing

Rotational Quantum Beat Lasing without Inversion

Recent Advances in Air Lasing: A Perspective from Quantum Coherence

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