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Light(Science & Applications) 2024年第2期13卷 354-365页

作者： Yaoxiang Liu Fukang Yin Tie-Jun Wang Yuxin Leng Ruxin Li Zhizhan Xu see leang chin State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics and CAS Center for Excellence in Ultra-intense Laser ScienceChinese Academy of SciencesShanghaiChina Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijingChina Centre d’Optique Photonique et Laser(COPL)and Département de physiquede génie physique et d’optiqueUniversitéLavalQuébecQuébecCanada

Supercontinuum(SC)light source has advanced ultrafast laser spectroscopy in condensed matter science,biology,physics,and *** to the frequently used photonic crystal fibers and bulk materials,femtosecond laser filamentation in gases is damage-immune for supercontinuum generation.A bottleneck problem is the strong jitters from filament induced self-heating at kHz repetition rate *** demonstrated stable kHz supercontinuum generation directly in air with multiple mJ level pulse *** was achieved by applying an external DC electric field to the air plasma *** pointing jitters of the 1 kHz air filament induced SC light were reduced by more than 2 *** stabilized high repetition rate laser filament offers the opportunity for stable intense SC generation and its applications in air.

关键词： intense repetition light

Lightning in a Forest (Wild) Fire: Mechanism at the Molecular Level

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Atmospheric and Climate Sciences 2024年第1期14卷 128-135页

作者： see leang chin Xueliang Guo Harmut Schroeder Huanbin Xu Tie-Jun Wang Ruxin Li Weiwei Liu Department of Physics and Center for Optics Photonics and Lasers (COPL) Laval University Quebec Canada Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Max Planck Institute of Quantum Optics Garching Germany State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai China Institute of Modern Optics Nankai University Tianjin China

The mechanism of lightning that ignites a forest fire and the lightning that occurs above a forest fire are explained at the molecular level. It is based on two phenomena, namely, internal charge separation inside the atmospheric cloud particles and the existence of a layer of positively charged hydrogen atoms sticking out of the surface of the liquid layer of water on the surface of rimers. Strong turbulence-driven collisions of the ice particles and water droplets with the rimers give rise to breakups of the ice particles and water droplets into positively and negatively charged fragments leading to charge separation. Hot weather in a forest contributes to the updraft of hot and humid air, which follows the same physical/chemical processes of normal lightning proposed and explained recently[1]. Lightning would have a high probability of lighting up and burning the dry biological materials in the ground of the forest, leading to a forest (wild) fire. The burning of trees and other plants would release a lot of heat and moisture together with a lot of smoke particles (aerosols) becoming a strong updraft. The condition for creating lightning is again satisfied which would result in further lightning high above the forest wild fire.

关键词： Forest Wild Fire Lightning Molecular Level

Population inversion in fluorescing fragments of super-excited molecules inside an air filament

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chinese Physics B 2015年第1期24卷 36-42页

作者： see-leang chin 徐淮良 Department of Physics Engineering Physics and Optics & Center for Optics Photonics and Laser (COPL)Laval University Quebec QC G1V 0A6 Canada State Key Laboratory on Integrated Optoelectronics College of Electronic Science and EngineeringJilin University

An original idea is reviewed. When a molecule is pumped into a super-excited state, one of its decay channels is neutral dissociation. One or more of the neutral fragments will fluoresce. Hence, if a lower state of such fluorescing fragments was populated through other channels but with a lower probability, population inversion of the fluorescing fragments would be naturally realized. This idea seems to be validated, so far, by comparing published work on three hydrocarbon molecules, CH4, C2H2, C2H4, and water vapor, H2 O. After super-excitation in a femtosecond laser filament in air mixed with these molecules, the fluorescence from the CH or OH fragments exhibits population inversion, i.e., amplified spontaneous emission was observed in the backscattering direction of the filament.

关键词： femtosecond filament lasing super-excited states

Understanding the beam self-cleaning behavior of ultrashort laser pulse filamentation

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Science china(Technological Sciences) 2007年第4期50卷 413-421页

作者： see leang chin Department of Physics Engineering Physics and Optics & Center for Optics photonics and Laser (COPL) Laval University Quebec Canada G1K 7P4

In this paper we report a recent study on the beam self-cleaning behavior occurred during the ultrashort laser pulse filamentation process. The propagation of a Gaussian beam with distorted beam profile is numerically simulated based on the nonlinear wave equation. Our results demonstrate that when the power is not too high so that multiple filaments are not yet induced, the intensity perturbation con-tained in the initial beam profile could be treated as high order spatial modes su-perpositioning on a fundamental mode. Then the self-focusing of the laser beam acts as a spatial filter. It focuses the fundamental mode toward the propagation axis, and produces a fundamental mode profile at the self-focus. While the strong diffraction of higher order modes could not be counteracted by the self-focusing. Therefore their propagation is mainly governed by the divergence without de-stroying the high profile quality at the self-focal region. These lead to the observa-tion of beam profile self-cleaning behavior.

关键词： filamentation ultrashort pulse self-cleaning

Intense broadband THz generation from femtosecond laser filamentation

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chinese Optics Letters 2013年第1期11卷 25-30页

作者： Tie-Jun Wang Shuai Yuan Yanping Chen see leang chin Centre d'Optique Photonique et Laser (COPL) and Département de Physique de Génie Physique et D'Optique Université Laval Québec

Broadband and energetic terahertz （THz） pulses can be remotely generated in air through filamentation. We review such THz generation and detection in femtosecond Ti-sapphire laser induced remote filaments. New results are presented on the direct relationship between THz generation in a two color filament and induced N2 fluorescence through population trapping during molecular alignment and revival in air. This further supports the new technique of remote THz detection in air through the sensitive measurement of N2 fluorescence.

关键词： THz Intense broadband THz generation from femtosecond laser filamentation

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强激光诱导的超激发态NO分子的中性解离

chinese Journal of Chemical Physics 2010年第3期23卷 252-254,I0001页

作者：刘凯宋迪 Ali Azarm see-leang chin 孔繁敖北京分子科学国家实验室中国科学院化学研究所分子动态与稳态结构国家重点实验室北京100190 拉瓦尔大学魁北克GIK7P4

利用波长800nm、脉宽60fs、强度0．2PW／cm^2的强激光激发NO分了，随后通过荧光光谱检测到了处于激发态的N和O的中性碎片．说明强激光导致的多光子激发同样可以引起NO分子的超激发，并且发生中性解离．采用离子实解离模型，建立了NO分... 详细信息

利用波长800nm、脉宽60fs、强度0．2PW／cm^2的强激光激发NO分了，随后通过荧光光谱检测到了处于激发态的N和O的中性碎片．说明强激光导致的多光子激发同样可以引起NO分子的超激发，并且发生中性解离．采用离子实解离模型，建立了NO分子的超激发态势能曲线．提出了直接解离和预解离两种解离过程，分别对应生成N^＊＋O或O^＊＋N两个通道．

关键词：超激发态中性解离强激光

Charging Mechanism of Lightning at the Molecular Level

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Atmospheric and Climate Sciences 2023年第4期13卷 415-430页

作者： see leang chin Xueliang Guo Harmut Schroeder Di Song Andong Xia Fan’ao Kong Huanbin Xu Tiejun Wang Ruxin Li Department of Physics and Center for Optics Photonics and Lasers (COPL) Laval University Quebec City Canada Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China Max Planck Institute of Quantum Optics Garching Germany State Key Laboratory of Information Photonic and Optical Communications School of Science Beijing University of Posts and Telecommunications (BUPT) Beijing China Institute of Chemistry Chinese Academy of Sciences Beijing China State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai China

Cloud electrification is one of the oldest unresolved puzzles in the atmospheric sciences. Though many mechanisms for charge separation in clouds have been proposed, a quantitative understanding of their respective contribution in a given meteorological situation is lacking. Here we suggest and analyze a hitherto little discussed process. A qualitative picture at the molecular level of the charge separation mechanism of lightning in a thundercloud is proposed. It is based on two key physical/chemical natural phenomena, namely, internal charge separation of the atmospheric impurities/aerosols inside an atmospheric water cluster/droplet/ice particle and the existence of liquid water layers on rimers (graupels and hailstones) forming a layer of dipoles with H+ pointing out from the air-water interface. Charge separation is achieved through strong collisions among ice particles and water droplets with the rimers in the turbulence of the thundercloud. This work would have significant contribution to cloud electrification and lightning formation.

关键词： Cloud Electrification Charge Separation Collision Molecular Level

Spectroscopic analysis of high electric field enhanced ionization in laser filaments in air for corona guiding

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High Power Laser Science and Engineering 2016年第1期4卷 52-57页

作者： Yingxia Wei Yaoxiang Liu Tie-Jun Wang Na Chen Jingjing Ju Yonghong Liu Haiyi Sun Cheng Wang Jiansheng Liu Haihe Lu see leang chin Ruxin Li State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine MechanicsChinese Academy of Sciences Centre d’Optique Photonique et Laser (COPL) and Dpartement de physiquede gnie physique et d’optiqueUniversit Laval

We report on a systematic experimental study on the fluorescence spectra produced from a femtosecond laser filament in air under a high electric field. The electric field alone was strong enough to create corona discharge(CD). Fluorescence spectra from neutral and ionic air molecules were measured and compared with pure high-voltage CD and pure laser filamentation(FIL). Among them, high electric field assisted laser FIL produced nitrogen fluorescence more efficiently than either pure CD or pure FIL processes. The nonlinear enhancement of fluorescence from the interaction of the laser filament and corona discharging electric field resulted in a more efficient ionization along the laser filament zone, which was confirmed by the spectroscopic measurement of both ionization-induced fluorescence and plasma-scattered 800 nm laser pulses. This is believed to be the key precursor process for filament-guided discharge.

关键词： femtosecond laser filamentation filament induced fluorescence spectroscopy laser guided discharges

Sub-picosecond chirped laser pulse-induced airflow and water condensation in a cloud chamber

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chinese Optics Letters 2018年第6期16卷 59-63页

作者：孙海轶刘永宏刘建胜鞠晶晶王成胡兴凯朱忠彬刘尧香王铁军 see leang chin 李儒新徐至展 State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine MechanicsChinese Academy of Sciences MOE Key Laboratory of Advanced Micro-structured Materials Institute of Precision Optical EngineeringSchool of Physics Science and Engineering Tongji University IFSA Collaborative Innovation Center Shanghai Jiao Tong University Center for Optics Photonics and Laser (COPL) Laval University

Sub-picosecond chirped laser pulse-induced airflow and water condensation were investigated in a cloud *** results indicate that the positively chirped sub-picosecond laser pulses generate a more uniform intensity distribution inside the plasma column, leading to a weaker airflow and an elliptic-shaped snow pile. The negatively chirped sub-picosecond laser pulses generate a spark-like intensity distribution inside the plasma column, which produces a wider range of airflow and a round snow pile. The amount of snow weight and the concentration of NO3-- are found to be dependent on the intensity distribution inside the plasma column. The visibly stronger plasma column generates much more snow and a higher concentration of NO3--. These experimental results provide a reference for sub-picosecond laser-induced water condensation in realistic atmospheric conditions.

关键词： Sub-picosecond chirped laser pulse-induced airflow and water condensation in a cloud chamber

Explosion of neutral molecules in intense laser fields

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Explosion of neutral molecules in intense laser fields