共查询到20条相似文献,搜索用时 281 毫秒
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为精确再现超强飞秒脉冲激光在大气中的传输特性,有效控制激光诱导等离子体通道的性能参数,基于扩展的非线性薛定谔方程,研究了空气中产生的等离子通道的演变过程。该模型在考虑衍射、色散和多光子效应的基础上,引入了拉曼散射、等离子体尾波场和相对论自聚焦等多种效应。讨论了电子密度和光强通量的空间分布特性,运用分步傅里叶法和有限差分法得到了电子密度和光强通量的分布,仿真结果显示,激光波长、单脉冲能量、脉宽和束腰半径等初始参数的变化将对等离子体通道的演变产生显著影响,为超短脉冲强激光在大气中成丝位置和形态控制提供了可能的途径。 相似文献
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利用基于液晶空间光调制器的飞秒激光脉冲整形技术,对飞秒激光在熔融石英中形成等离子体丝的过程进行优化控制研究。实验结果表明:通过脉冲整形可以在固体介质中的指定位置产生等离子体丝。实现了整形脉冲在熔融石英中成丝起点的长距离可控移动,最大移动量达到5.4 mm。通过求解(3+1)维非线性薛定谔方程,对整形脉冲在熔融石英中的成丝过程进行理论模拟研究,得到了与实验一致的结果。研究结果表明:等离子体丝起始位置是由整形飞秒脉冲的中心峰值强度和包络分布决定的。 相似文献
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利用皮秒和飞秒激光研究了激光在空气中聚焦产生单个等离子体通道的条件.研究发现,能量为8—12mJ皮秒激光被焦距为15cm的透镜聚焦后,可以产生较为稳定的单个通道.通过横向纵向阴影成像分析发现,通道的管壁对聚焦产生的自发光具有箍缩作用,而通道内部却有利于光的传输.同时还发现,当采用短焦距透镜时,能量低于10mJ的飞秒激光在空气中较易形成单个等离子通道.
关键词:
等离子体通道
皮秒激光
飞秒激光
阴影成像 相似文献
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采用能够较为清晰、完整描述强飞秒激光等离子体通道内带电粒子产生过程及其演化的物理模型,进一步研究了飞秒光丝中等离子体密度的时间演化特征。计算结果表明:对于不同时间线型的脉冲,在等离子体通道形成过程中,氧气分子的电离贡献率及氮气分子的贡献率明显不同,不同线型的脉冲对高效维持高密度等离子体的寿命具有较大的影响。有效控制成丝脉冲线型能够达到对等离子体通道的高效利用。长脉冲、短波长虽能够获得较高密度等离子体通道,但其存活寿命却完全受限于通道的后期演化。 相似文献
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《光子学报》2015,(9)
利用飞秒脉冲诱导生成的具有渐变折射率分布的等离子体通道产生空心光束.当飞秒脉冲在非线性介质中传输时将电离产生等离子体通道,该等离子体通道具有渐变的折射率分布,等离子体通道中激光束只能在电子密度低于临界等离子体密度的区域传播,故当探测光束在等离子体通道边缘传输时将偏转形成空心光束.当泵浦光束功率为8mW时,探测光束转变为典型的空心光束结构;当泵浦光束的入射功率、重复率或等离子体通道中轴向电子密度改变时,等离子体通道中可供探测光束通过的区域将随之发生改变,这将导致空心光束中黑斑的面积发生变化.因此通过调节泵浦光束的入射功率和重复率可以控制产生空心光束的黑斑大小. 相似文献
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The multiple filamentation of terawatt femtosecond(fs) laser pulses is experimentally studied in a natural environment.A more than 30-m long plasma filament with a millimeter diameter is formed by the collimated fs laser pulse freely propagating in an open atmosphere. This study provides the first quantitative experimental data about the electron density of a long range light filament in the atmosphere. The electron density of such a filament is quantitatively detected by using an electric method, showing that it is at the 10~(11)-cm~(-3) level. 相似文献
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Optical breakdown and filamentation of femtosecond laser pulses propagating in air at a kHz repetition rate 总被引:1,自引:0,他引:1 下载免费PDF全文
We report the experiments on the optical breakdown and filamentation of femtosecond laser pulses propagating in air at a kHz repetition rate and with several hundreds micro-joule-energy.A 10m-long filament and its breakup and merging at the nonlinear focal region produced by modulational instability of femtosecond laser pulses in air are observed.A simple model based on the nonlinear Schroedinger equation coupled with multiphoton ionization law is presented to explain the several experimental results. 相似文献
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Backward supercontinuum emission from a filament generated by ultrashort laser pulses in air 总被引:1,自引:0,他引:1
Yu J Mondelain D Ange G Volk R Niedermeier S Wolf JP Kasparian J Sauerbrey R 《Optics letters》2001,26(8):533-535
Backward emission of the supercontinuum from a light filament induced by high-intensity femtosecond laser pulses propagating in air has been observed to be enhanced compared with linear Rayleigh-Mie scattering. This enhancement is interpreted as a nonlinear scattering process onto longitudinal refractive-index changes induced by the laser pulse itself. The spectral dependence of the supercontinuum angular distribution is also investigated. 相似文献
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I. V. Blonskii V. N. Kadan O. I. Shpotyuk I. N. Dmitruk I. A. Pavlov 《JETP Letters》2009,89(11):535-539
The transformation of a femtosecond laser pulse propagating in fused quartz before and after its transition to a filamentation regime has been investigated by femtosecond time-resolved optical polarigraphy. The spatial periodicity of a light field along and across the propagation axis has been detected and its nature has been attributed to the interference of the conical and plane components of the wave packet of the filament. The “supraluminal” motions of the observed filament intensity maximum are due to the longitudinal transformation of the pulse profile. 相似文献
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Calegari F Vozzi C Gasilov S Benedetti E Sansone G Nisoli M De Silvestri S Stagira S 《Physical review letters》2008,100(12):123006
The spatiotemporal effects generated in the wake of a laser filament propagating in nitrogen are investigated. At suitable time delays, a probe light pulse propagating along the wake experiences a strong spatial confinement and a noticeable spectral broadening at the same time. Numerical simulations, well reproducing the experimental findings, show the key role of the impulsive rotational Raman response in the observed phenomena. 相似文献
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Self-transformation of a powerful femtosecond laser pulse into a white-light laser pulse in bulk optical media (or supercontinuum generation) 总被引:2,自引:0,他引:2
V.P. Kandidov O.G. Kosareva I.S. Golubtsov W. Liu A. Becker N. Akozbek C.M. Bowden S.L. Chin 《Applied physics. B, Lasers and optics》2003,77(2-3):149-165
We present experimental and theoretical results on white-light generation in the filamentation of a high-power femtosecond laser pulse in water and atmospheric air. We have shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation, is sustained due to the dynamic transformation of the light field on the whole transverse scale of the beam, including its edges. We found that the sources of the supercontinuum blue wing are in the rings, surrounding the filament, as well as at the back of the pulse, where shock-wave formation enhanced by self-steepening takes place. We report on the first observation and demonstration of the interference of the supercontinuum spectral components arising in the course of multiple filamentation in a terawatt laser pulse. We demonstrate that the conversion efficiency of an initially narrow laser pulse spectrum into the supercontinuum depends on the length of the filament with high intensity gradients and can be increased by introducing an initial chirp. PACS 42.65.Jx; 42.65.Re; 42.25.Bs; 42.50.Hz 相似文献
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One has prospected to overcome the intensity clamping phenomenon during femtosecond laser filamentation by superimposing two
beams. This experimental scheme is thus studied in our work. We have realized the interference of two ultrashort laser beams
and one of them creates a filament in air. The formation of a dynamic plasma grating induced by the interference pattern is
observed. However, qualitative analysis of the experimental results indicates that intensity clamping still governs the intensity
evolution during the dual-beam interaction. The expectation of greatly increasing laser intensity by dual beams superposition
might not be realistic. 相似文献
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Yang H Zhang J Zhang Q Hao Z Li Y Zheng Z Wang Z Dong Q Lu X Wei Z Sheng Z Yu J Yu W 《Optics letters》2005,30(5):534-536
We investigate polarization-dependent properties of the supercontinuum emission generated from filaments produced by intense femtosecond laser pulses propagating through air over a long distance. The conversion efficiency from the 800-nm fundamental to white light is observed to be higher for circular polarization than for linear polarization when the laser intensity exceeds the threshold of the breakdown of air. 相似文献
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原则上,激光腔中相干光的强度应由往返光束按场强叠加计算。本文比较按场强叠加和通常按光强叠加的计算,指出:腔中各处的饱和增益和光强确有可观的偏差,但场分布和输出功率很好地相符。
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