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1.
蔡怀鹏  高健  李博原  刘峰  陈黎明  远晓辉  陈民  盛政明  张杰 《物理学报》2018,67(21):214205-214205
超短超强激光与固体靶表面等离子体相互作用可以通过高次谐波的方式产生从极紫外到软X射线波段的相干辐射,获得飞秒甚至阿秒量级的超短脉冲,可用于观测原子或分子中的电子运动等超快动力学过程.本文实验研究了相对论圆偏振飞秒激光与固体靶相互作用的高次谐波产生过程,实验结果表明,在较大入射角下,圆偏振激光也可以有效地产生高次谐波辐射.通过预脉冲控制靶表面的预等离子体密度标长,发现高次谐波的产生效率随密度标长的增加而单调下降.进一步通过二维粒子模拟程序,分析了激光的偏振以及预等离子体密度标长对高次谐波产生的影响,很好地解释了实验观测结果.  相似文献   

2.
李夏至  邹德滨  周泓宇  张世杰  赵娜  余德尧  卓红斌 《物理学报》2017,66(24):244209-244209
极紫外光和软X射线由于其波长和脉冲持续时间极短,可用于超快物理过程和物质微观结构的探测.最近几年,研究人员发现激光和等离子体相互作用可以产生持续时间极短(阿秒)且相干性较好的高次谐波辐射,其波长可接近甚至达到水窗波段.然而,实验研究指出,理论上应出现的一些谐波在实验中并没有出现.本文针对超短超强激光与非理想条件下的等离子体光栅靶相互作用产生高次谐波的物理过程进行了理论分析和粒子模拟.研究结果表明,等离子体光栅的周期性结构对于高次谐波的频谱和辐射角分布存在显著调制效果.光栅靶表面粗糙度直接影响光栅的光学调制效果,改变高次谐波的频谱分布和辐射角分布.理想光栅条件下,满足光栅匹配条件的特定阶数谐波明显获得增强,且辐射张角集中在平行靶面的方向.靶表面粗糙度的出现,导致光栅匹配条件失效,高次谐波能量向各阶分散且辐射张角逐渐偏离靶表面方向.研究结果较好地解释了实验中观测到的谐波频谱分布,为进一步的研究提供了一定参考.  相似文献   

3.
王超  康轶凡  白永林  王屹山  徐鹏  王向林 《强激光与粒子束》2018,30(10):101001-1-101001-4
为提高强激光场与惰性气体靶作用产生的孤立阿秒激光脉冲的能量,给出了一种实现高次谐波过程中最佳谐波相位匹配的定量实验方法。研究了气体靶源与高斯型驱动激光场聚焦点相对空间位置对谐波相位匹配及谐波产率的影响,得出了其最佳相位匹配位置始终位于驱动激光场聚焦点后3~5 mm,而在聚焦点之前的位置区域,严重的高次谐波相位失配导致谐波产率非常低。同时,在最佳相位匹配条件下,高次谐波场与驱动场具有相类似的空间强度分布特性,该结果印证了目前通常采用的高次谐波场为高斯光束的假设。  相似文献   

4.
飞秒激光脉冲在氮气中产生高次谐波的实验研究   总被引:1,自引:0,他引:1  
陈建新  夏元钦  姚琴  王骐 《光学学报》2002,22(6):50-653
报道了以氮气为介质产生高次谐波的实验结果。实验中主要研究了不同的气体密度、不同入射激光能量和不同偏振对高次谐波辐射强度及谐波级次的影响。并从理论上进行了定性分析。分析结果表明:要想得到较高次、较强的谐波辐射,必须反复进行实验,确定最佳的激光能量和气体密度,以减少由于自由电子密度的提高而导致的相位失配的影响。  相似文献   

5.
氩气中高次谐波辐射的研究   总被引:4,自引:0,他引:4  
报道了在45fs-2TW激光装置上以Ar惰性气体为介质产生高次谐波的实验结果,实验中通过研究气体密度和激光能量对谐波辐射的影响,找到了适当的气体密度和激光能量范围,并在Ar气中观察到81次(9.7nm)的皆波辐射,这时迄今为止,人们在Ar气中所能观测到的最短波长的谐波辐射,经分析表明,高于57次的谐波是由Ar离子产生的。  相似文献   

6.
介质的非均匀性对高次谐波影响的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
讨论了气体介质的非均匀性对飞秒激光高次谐波产生过程的可能影响.计算结果表明,采用喷阀技术所提供的气体介质的密度梯度和气体原子运动速度的影响很小,不会产生实验上可观测的效果.这一结果支持了喷气靶在高次谐波产生中的广泛应用 关键词: 高次谐波 气体介质 各向异性 飞秒激光  相似文献   

7.
强场高次谐波辐射过程中的相位匹配   总被引:2,自引:0,他引:2  
从实验上定性地研究了强 辐射过程中位相匹配的作用与影响,主要通过改变气体密度、激光强度和光束的共焦参数来研究相位对高闪谐波辐射的影响。从改善高次谐波辐射过程中的相位匹配来考虑,气体攻激光强度都有一最佳值。利用大的共焦参数,可以明显改善相位匹配,提高谐波输出的转换效率。  相似文献   

8.
汪礼锋  贺新奎  滕浩  运晨霞  张伟  魏志义 《物理学报》2014,63(22):224103-224103
研究了在紧聚焦实验条件下, 采用5 fs激光脉冲与氩气相互作用产生的高次谐波特性. 通过优化系统色散、气体靶气压与位置等参数, 观察到在60–73 eV波段范围内高次谐波光谱接近一个量级的增强. 进一步通过对单原子模型和传播方程的数值求解及模拟相位匹配实验参数下高次谐波的产生过程, 发现相位匹配在所观察到的实验现象中起着关键作用, 得到了理论上与实验规律一致的结果. 关键词: 极紫外激光 高次谐波 超快光谱  相似文献   

9.
超短脉冲强激光与固体靶作用产生的高次谐波红移   总被引:1,自引:0,他引:1       下载免费PDF全文
张秋菊  盛政明  张杰 《物理学报》2004,53(7):2180-2183
用一维粒子模拟程序研究了超短脉冲强激光与超临界密度等离子体平板作用产生的高次谐波。分析了振荡镜面模型所不能解释的伴随高次谐波出现的频率红移现象。通常激光与固体靶作用中的高次谐波是由于激光从振荡靶面的反射产生的.除此之外,相对论光强的激光与固体靶作用还应考虑光压对靶的烧蚀推进作用,这时激光相当于从一个移动的振荡靶面反射,所以产生了带有红移的高次谐波. 关键词: 红移 超短脉冲强激光 高次谐波 粒子模拟  相似文献   

10.
超强激光场中氢原子辐射高次谐波蒙特卡罗模拟   总被引:1,自引:1,他引:0  
运用蒙特卡罗方法,模拟和计算出在超强激光场中,氢原子在相对论领域的电离几率和辐射出的高次谐波,并且讨论了氢原子的电离几率和辐射出的高次谐波与激光场的电场和磁场的关系。  相似文献   

11.
A xenon flash-lamp-pumped, passively Q-switched Nd:GdVO4 laser with GaAs semiconductor saturable absorber is demonstrated. The static laser performance is investigated and the static output is 52 mJ when the pump energy is 9.45 J. The dynamic laser has the highest slope efficiency when the GaAs wafer is both the saturable absorber and output coupler. Pulses with duration of 64 ns and dynamic output of 47.6 mJ are obtained when the pump energy is 9.45 J. The highest dynamic–static ratio is 0.9:1. The coupled rate equations are used to simulate the Q-switched process of laser. The theoretical and experimental results are compared and discussed.  相似文献   

12.
The 5th - 23sd high-order harmonics generation in rare gases in static gas target with 120-fs, 85-m J/pulse,10-Hz laser system was investigated. Compared with the traditional gas target, static gas target is simple to be used in experiment, and the experimental parameters can be easily controlled. The effects on highorder harmonics due to laser intensities (energy), polarization, gas densities, confocal parameter, and phase mismatch were studied in this paper.  相似文献   

13.
Previous experimental studies showed that powerful heating of nanoparticles by a laser pulse using energy density greater than 100 mJ/cm2, could induce vaporization and generate microbubbles. When ultrasound is introduced at the same time as the laser pulse, much less laser power is required. For therapeutic applications, generation of microbubbles on demand at target locations, e.g. cells or bacteria can be used to induce hyperthermia or to facilitate drug delivery. The objective of this work is to develop a method capable of predicting photothermal and acoustic parameters in terms of laser power and acoustic pressure amplitude that are needed to produce stable microbubbles; and investigate the influence of bubble coalescence on the thresholds when the microbubbles are generated around nanoparticles that appear in clusters.

We develop and solve here a combined problem of momentum, heat and mass transfer which is associated with generation and growth of a microbubble, filled with a mixture of non-vaporized gas (air) and water vapor. The microbubble’s size and gas content vary as a result of three mechanisms: gas expansion or compression, evaporation or condensation on the bubble boundary, and diffusion of dissolved air in the surrounding water. The simulations predict that when ultrasound is applied relatively low threshold values of laser and ultrasound power are required to obtain a stable microbubble from a single nanoparticle. Even lower power is required when microbubbles are formed by coalescence around a cluster of 10 nanoparticles. Laser pulse energy density of 21 mJ/cm2 is predicted for instance together with acoustic pressure of 0.1 MPa for a cluster of 10 or 62 mJ/cm2 for a single nanoparticle. Those values are well within the safety limits, and as such are most appealing for targeted therapeutic purposes.  相似文献   


14.
We present results on development and experimental implementation of a 1-kHz, coherent extreme ultraviolet (XUV) radia- tion source based on high-order harmonic generation of the femtosecond, near-infrared laser pulses produced by the titanium-doped sapphire laser system (35 fs, 1.2 mJ, 810 nm) at the Institute of Physics AS CR / PALS Centre. The source comprises a low-density static gas cell filled with a conversion medium, typically argon. The comprehensive optimization of the XUV harmonic source has been performed with respect to major parameters such as gas pressure in the cell, cell length, position of the focus of the driving laser field with respect to the gas cell position, size of the driving near-infrared laser beam, chirp of the femtosecond pulse, and the focal length of the lens deployed in the experimental setup. Harmonic spectra were recorded using an XUV transmission grating spectrometer developed specifically for this purpose. Detailed characterization of the XUV source has been performed including measurement of the XUV beam profile, M2 parameter of the beam, absolute energy, and spatial coherence.  相似文献   

15.
The high repetition rate capability of a discharge pumped XeCl laser with static fill has been studied by double pulse experiments. By suitably selecting the laser parameters (energy deposition, gas mixture composition, filling pressure), following an analytical model of the discharge induced thermal effects, laser action from the second pulse for delays as short as 5 ms with an energy of 12.5 mJ has been achieved.  相似文献   

16.
研究了不同条件下脉冲放电CO2激光烧蚀平板锡靶产生的等离子体极紫外辐射特性,设计并建立了一套掠入射极紫外平焦场光栅光谱仪,结合X射线CCD探测了光源在6.5~16.8nm波段的时间积分辐射光谱,得到了极紫外光谱随激光脉宽,入射脉冲能量及背景气压的变化规律。实验结果发现:入射激光脉冲能量在30~600mJ变化时,极紫外辐射光谱的强度随辐照激光脉冲能量的增加而增加,但并不是线性关系,具有饱和效应,且产生极紫外辐射的脉冲能量阈值约为30mJ,当激光脉冲能量为425mJ时具有最高的转换效率,此时中心波长13.5nm处2%带宽内的转换效率约为1.2%。激光脉冲半高全宽在50~120ns范围内变化时,极紫外辐射光谱的峰值位置均位于13.5nm,光谱形状几乎没有什么变化,但是脉宽从120ns变到52ns后,由于激光功率密度的提高,极紫外辐射强度也随之增强了约1.6倍。极紫外光谱的强度随背景气压的增大而迅速下降,当腔内空气气压为200Pa时,极紫外辐射光子几乎被全部吸收,而当缓冲氦气气压为7×104 Pa时,仍能够探测到微弱的极紫外辐射信号,计算表明100Pa的空气对13.5nm极紫外光的吸收系数为3.0m-1,而100Pa的He气的吸收系数为0.96m-1。  相似文献   

17.
激光脉冲能量对激光诱导Al等离子体辐射特征的影响   总被引:3,自引:0,他引:3  
使用Nd:YAG激光器烧蚀金属Al靶获得等离子体,利用光谱时-空分辨技 术,在52 mJ~145 mL/pulse激光脉冲能量范围内,关于激光脉冲能量对激光诱导等离子体 辐射特征的影响进行了研究。使用的气体是Ar气,压强为10 kPa。结果发现,激光脉冲能量 升高,引起特征谱线强度增加,连续谱强度也增加;但能量过高,会击穿周围气体,产生气 体微等离子体。此时,特征谱和连续谱几乎不再增强;最大特征辐射强度在145 mJ、10 kPa 、靶前0.1 mm处、延时180 ns获得;同一条件下获得最强背景连续谱,而信号-背景差是在 145 mJ、10 kPa、靶前1.0 mm处、延时450 ns达到最大值。基于Al等离子体不同激光脉冲能 量下的时间-空间分辨谱,对结果进行了简单的讨论。并分别确定了获得最大特征辐射和信 号-背景差的条件。  相似文献   

18.
High-order harmonics are generated by coherent interaction of an intense laser and atoms or molecules[1]. With the development of the intense ultrashort pulse laser, the research of high-order harmonic generation has reached the water-window in spectral region[2] and subfemtosecond in time domain[3]. Especially, the generation and application of subfemtosecond pulse led the study of high-order harmonic generation into a completely new world[4, 5]. It has made the study of ultrafast science fro…  相似文献   

19.
纳秒激光在铜靶材中诱导冲击波的实验研究   总被引:1,自引:0,他引:1       下载免费PDF全文
王绩勋  高勋  宋超  林景全 《物理学报》2015,64(4):45204-045204
基于聚偏二氟乙烯压电传感器, 对铜靶材中纳秒激光脉冲诱导的冲击波传播过程进行了实验研究, 给出了铜靶材内冲击压强随激光脉冲能量和靶材厚度的变化规律. 实验结果表明: 500 mJ激光脉冲能量作用到2 mm厚的铜靶材产生的冲击压强达到2.1 MPa; 激光脉冲能量从200 mJ 增加到500 mJ, 在铜靶材厚度为2和4 mm条件下, 冲击压强分别增加了162%和231%; 而当铜靶材厚度从2 mm增加到6 mm时, 在400和500 mJ激光脉冲能量作用下, 铜靶材内冲击压强分别降低了32%和49%.  相似文献   

20.
The dynamics of a titanium plasma species, induced in air by coupling a fs-ablating laser pulse with an orthogonal ns-reheating laser source placed at the fixed distance of 1.0 mm from the target surface, has been followed by temporally resolved emission spectroscopy. The temporal evolutions of plasma features such as excitation temperatures and electron densities have been evaluated by using two different laser energies of the first fs-ablating laser pulse (0.8 mJ and 3.0 mJ). Optimum inter-pulse delay times, experimentally determined, of 250 μs and 500 μs were used for the fs laser energy of 3.0 mJ and 0.8 mJ, respectively. By experimental inspections of the main plasma species electronic transitions so obtained, a strong enhancement was evaluated up to one and two orders of magnitude for Ti(I) and Ti(II), respectively. Independently from the fs laser energy employed, the plasma features showed the same temporal behaviour implying that the ns-reheating characteristics of this process belong to the reheating mechanism itself. The experimental results have been discussed and the excited species evolutions and elementary processes involved, as well as, the local thermodynamic equilibrium departures, have been outlined.  相似文献   

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