その他 Sub-10-fs population inversion in N2+ in air lasing through multiple state coupling

Xu, Huailiang  ,  Lötstedt, Erik  ,  Iwasaki, Atsushi  ,  Yamanouchi, Kaoru

62015-09-25 , Nature Publishing Group , Department of Chemistry, School of Science, The University of Tokyo , State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University
ISSN:2041-1723 (online)
NII書誌ID(NCID):AA12645905
内容記述
UTokyo Research掲載「レーザーが空気中で増幅される機構を解明」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/mechanism-of-air-lasing.html
UTokyo Research "Mechanism of air lasing" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/mechanism-of-air-lasing.html
Laser filamentation generated when intense laser pulses propagate in air has been an attractive phenomenon having a variety of potential applications such as detection and spectroscopy of gases at far distant places. It was discovered recently that the filamentation in air induces ‘lasing’, showing that electronically excited N2+ is population-inverted, exhibiting marked contrast to the common understanding that molecular ions generated by intense laser fields are prepared mostly in their electronic ground states. Here, to clarify the mechanism of the population inversion, we adopt few-cycle laser pulses, and experimentally demonstrate that the lasing at 391 nm occurs instantaneously after N2+ is produced. Numerical simulations clarify that the population inversion is realized by the post-ionization couplings among the lowest three electronic states of N2+. Our results shed light on the controversy over the mechanism of the air lasing, and show that this post-ionization coupling can be a general mechanism of the atmospheric lasing.
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http://repository.dl.itc.u-tokyo.ac.jp/dspace/bitstream/2261/58564/1/ncomms9347.pdf

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