共查询到20条相似文献,搜索用时 0 毫秒
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J. Bernhardt W. Liu F. Théberge H.L. Xu M. Châteauneuf S.L. Chin 《Optics Communications》2008,281(5):1268-1274
We report a spectroscopic analysis of a filament generated by a femtosecond laser pulse in air. In the filament spectra, the characteristic Stark broadened atomic oxygen triplet centered at 777.4 nm has been observed. The measured electron impact Stark broadening parameter of the triplet is larger than the theoretical value by Griem [H.R. Griem, Plasma Spectroscopy, McGraw Hill, New York, 1964] by a factor 6.7. Using the experimental value , the plasma densities derived from Stark broadening agree well with those most recently obtained from Théberge et al.’s measurement of the nitrogen fluorescence calibrated by longitudinal diffraction [F. Théberge, W. Liu, P.T. Simard, A. Becker, S. L. Chin, Phys. Rev. E 74 (2006) 036406]. However, the Stark broadening approach is much simpler and can be used to non-invasively measure the filament plasma density distribution in air under different propagation conditions. 相似文献
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对中心波长为800 nm,脉宽为100 fs的激光脉冲烧蚀空气中硅(111)产生的等离子体发射光谱进行了时间和空间分辨研究. 结果表明,在等离子体羽膨胀初期(小于50 ns时间范围内),等离子体发射光谱主要由连续光谱构成,此后连续光谱强度逐渐减弱,线状光谱开始占主导地位;在羽体膨胀过程中离子谱线的存在时间短于原子谱线的存在时间. 由时间分辨发射光谱发现在羽体膨胀过程中等离子体辐射波长存在红移现象,波长红移量随时间演化呈二次指数衰减. 最后给出等离子体发射光谱谱线强度的时空演化规律.
关键词:
飞秒激光
脉冲激光烧蚀
等离子体
发射光谱 相似文献
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对强飞秒激光聚焦在空气中所激发的等离子体的发射光谱进行了实验研究.结果表明,光谱特征表现为短波段(截至波长为340 nm)强烈的连续谱和长波段(波长在800 nm附近)强度相对较低的线光谱.在脉冲宽度(50 fs)保持不变而不断调节激光脉冲能量时,等离子体光谱形状的特征基本相似;当激光脉冲能量(1 mJ)保持不变而脉冲宽度从50 fs增加至500 fs和1 ps时,连续谱的峰值(500 nm)显得格外突出,并开始呈现出线光谱特征.
关键词:
飞秒激光
激光空气等离子体
发射光谱
线光谱 相似文献
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M. Kurata-Nishimura T. Kobayashi T. Motobayashi J. Kawai 《Applied Surface Science》2009,255(24):9729-9733
Direct observations of ablation plasma dynamics in electric field is presented. A time-resolved spatial profile of the ablation plasma induced by femtosecond laser ablation (fsLA) with high fluence is visualized using a planar-laser-induced fluorescence (P-LIF) method. The external electric field is produced by installing a mesh electrode at 6 mm from a Samarium solid target. The Sm ion plasma created by the fsLA showed collective motion regardless of the external electric field, until they reached close to the electrode. When the accelerating and decelerating field was applied, the ions almost disappeared behind the electrode from the field of view. The observations are understood utilizing a SIMION simulation with a conceivable potential gradient caused by Debye shield effect, which is that the ablation plasma keeps the same potential as the target voltage and follows electric potential gradient near the mesh electrode. It is also revealed that this effect degrades time-of-flight resolution at high fluence irradiation. This work gives a new direction for further developments of a fsLA time-of-flight spectrometer. 相似文献
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Deng YP Zhu JB Ji ZG Liu JS Shuai B Li RX Xu ZZ Théberge F Chin SL 《Optics letters》2006,31(4):546-548
We investigate the evolution of filamentation in air by using a longitudinal diffraction method and a plasma fluorescence imaging technique. The diameter of a single filament in which the intensity is clamped increases as the energy of the pump light pulse increases, until multiple filaments appear. 相似文献
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A periodic structure is induced at the surface of a metal target exposed to a series of p-polarized 200-femtosecond laser pulses with intensity close to the melting threshold of the target material. The period of the structure is determined by the interference between the incident pump wave and the surface electromagnetic wave. Exposure of the obtained structure to the same laser pulse, but with an intensity of ~1016 W/cm2, provides resonant excitation of the surface electromagnetic waves at the plasma-vacuum interface. This leads to an increase in the X-ray output and the temperature of plasma hot electrons. 相似文献
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The influence of temporal pulse shaping on plasma plume generated by ultrafast laser irradiation of aluminum is investigated. Time resolved plasma emission spectroscopy is coupled with a temporal shaping procedure in a closed loop. The ionic emission is enhanced relative to the neutral one via an adaptive optimization strategy. The plasma emission efficiency in case of optimized and ultrashort temporal shapes of the laser pulses are compared, evidencing an enhancement of the ionization degree of the plasma plume. Simplified temporal shapes of the femtosecond laser pulses are extracted from the optimized shape and their corresponding effect on laser induced plasma emission is discussed. 相似文献
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文章从激光等离子体相互作用的非线性薛定谔方程出发,理论研究了飞秒强激光脉冲在等离子体中的自压缩行为.结果表明在一定范围内随着激光脉冲宽度、激光强度的增大以及等离子体密度的减小,飞秒强激光脉冲在等离子体中传播的自压缩现象越明显.另外通过适当设定参量得到了近似稳定传播的基孤子. 相似文献
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Prolongation of the fluorescence lifetime of plasma channels in air induced by femtosecond laser pulses 总被引:3,自引:0,他引:3
Z. Q. Hao J. Zhang Y. T. Li X. Lu X. H. Yuan Z. Y. Zheng Z. H. Wang W. J. Ling Z. Y. Wei 《Applied physics. B, Lasers and optics》2005,80(4-5):627-630
The lifetime of plasma channels induced by femtosecond laser pulses is investigated by detecting the decay time of the fluorescence signals from ions. It is found that the lifetime of the plasma can be prolonged to the order of microseconds when an additional sub-nanosecond laser pulse is injected into the channel. This prolongation is due to the heating and further ionization through the inverse bremsstrahlung absorption of the post-pulse. 相似文献
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Microscopic analysis of carbon phases induced by femtosecond laser irradiation on single-crystal SiC
Takuro Tomita Tatsuya Okada Hiroyuki Kawahara Ryota Kumai Shigeki Matsuo Shuichi Hashimoto Masako Kawamoto Makoto Yamaguchi Shigeru Ueno Emi Shindou Akira Yoshida 《Applied Physics A: Materials Science & Processing》2010,100(1):113-117
Elemental analysis of femtosecond laser-induced modified region was carried out by transmission electron microscopy and Raman spectroscopy. The relative Raman intensities of a-SiC were higher in the peripheral region of laser irradiated spot where the fine ripple was formed. On the contrary, the relative Raman intensities of a-Si were higher in the central region where the coarse ripple was formed. This result suggests that the material migration has strongly occurred in the higher fluence region. On the other hand, the mapping of carbon atoms in the topmost amorphous layer of laser induced periodic structures did not show any significant segregation. In addition, Raman spectroscopic analysis showed that the domain size of carbon was very small (< 1 nm). From these facts, it was found that the carbon atoms were uniformly distributed in the topmost amorphous layer and were randomly connected without forming any observable fine particles. 相似文献