为了探究飞秒激光成丝的内在机制以实现长度表征, 采用荧光法和声学法, 得到了不同入射激光脉冲能量下和偏振态下等离子体光丝的荧光光谱和声音信号信息。结果表明,在相同激光脉冲能量下圆偏振光产生的N2荧光信号强度约为线偏振光的2倍, 而线偏振光产生的N2+荧光信号强度则约为圆偏振光的1.3倍; 等离子体荧光测量是获取等离子体光丝长度的有效途径, 相比于声学测量法更精确。该研究为揭示相干激光发射随光丝长度变化的物理实质提供了光丝长度表征的可行方案。
激光物理 等离子体光丝 荧光强度演化 声学测量 laser physics plasma filament evolution of fluorescence intensity acoustic measurement
为了快速定量地分析待测样品中铀元素含量信息, 采用激光诱导击穿光谱技术结合内标法, 通过脉宽为7ns、输出能量为20mJ的纳秒激光脉冲诱导涂有硝酸双氧铀的石墨片产生等离子体光谱, 测量了波长范围为300nm~800nm的光谱数据, 对涂有不同浓度的铀样品进行了定量分析以及理论分析和实验验证, 取得了UⅡ 409.01nm和UⅡ 367.01nm谱线和CⅠ 373.72nm, CⅡ 383.57nm, CⅢ 378.94nm谱线数据。结果表明, 样品浓度低于5.0×10-3mol/m2(本文中研究的是面密度)时, 铀归一化强度与铀浓度存在较好的线性关系, 激光诱导击穿光谱技术与内标法结合可以用于快速定量分析待测样品中铀元素含量信息。该研究为核污染和铀矿中微量铀元素的快速检测分析提供了参考。
激光技术 激光诱导击穿光谱 硝酸双氧铀 定量分析 laser technique laser-induced breakdown spectroscopy uranyl nitrate quantitative analysis
Author Affiliations
Abstract
School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
The propagation of a filamentary laser beam at an air-glass surface is studied by setting the incident angle satisfying the total reflection condition. The images of the trajectory of the filamentary laser beam inside the sample and the output far-field spatial profiles are measured with varying incident laser pulse energies. Different from the general total reflection, a transmitted laser beam is detected along the propagation direction of the incident laser beam. The energy ratio of the transmitted laser beam depends on the pulse energies of the incident laser beam. The background energy reservoir surrounding the filament core can break the law of total reflection at the air-glass surface, resulting in the regeneration of the transmitted laser beam.
140.3440 Laser-induced breakdown 100.6640 Superresolution 210.4770 Optical recording 180.1790 Confocal microscopy Chinese Optics Letters
2017, 15(2): 021401
Author Affiliations
Abstract
School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
From a classical dynamic simulation, we find the kinetic energy of the electrons generated during laser plasma generation depends on the laser polarization and intensity. The electron kinetic energy reaches its maximum with a fixed laser intensity for circularly polarized laser pulse. The fluorescence spectra at 380.4 nm from N2 and 391.3 nm from N2+ are measured; these are generated by both the direct excitation and electron collision excitation. The electron collision excitation is determined by the electron energy and reaches the maximal with a circularly polarized pulse.
020.2649 Strong field laser physics 020.2070 Effects of collisions 300.6365 Spectroscopy, laser induced breakdown Chinese Optics Letters
2016, 14(11): 110201
为了实现红外飞秒脉冲的整形及调控, 采用4f系统相位控制技术, 实验搭建了脉冲整形装置, 并利用整形脉冲对铷原子体系中激发双重态间的相干布居转移进行操控。结果表明, 控制抽运脉冲的附加相位, 可实现双重态中上激发态的饱和布居, 通过修改附加相位函数可将上、下激发态的布居数反转。整形脉冲同样适用于其它的原子和分子系统的相干布居转移的操控。
激光物理 激发双重态 整形脉冲 相干布居转移 laser physics the excited double states pulse shaping coherent control of population transfer
为了实现调节两束飞秒激光脉冲在时间和空间区域上的精确重合, 采用利用CCD成像系统调节光束在空间上的重合及利用能量计测量激光脉冲核心能量变化来调节飞秒脉冲间的时间间隔的新方法, 取得了核心能量随延迟时间变化的数据, 并记录了相应的等离子体荧光图像。结果表明, 与传统方法相比, 这种方法可以达到飞秒级的时间重合精度。这为确定激光的时空重合提供了一种简便有效的途径, 且在激光光束以大角度相交时仍然可以确定最佳重合点。
激光技术 延迟时间调节 核心能量 能量计 laser technique time delay adjusting core energy energy meter
为了研究超短激光脉冲光束质量对焦斑的影响, 采用经典的几何模型进行了理论模拟分析, 并实验研究了离轴90°抛物面镜的飞秒激光光束的紧聚焦特性。由理论分析和实验结果可知, 当入射失准角为3mrad时, 将从空间上使焦斑峰值功率密度减半, 失准角的存在将引起到达靶面的激光脉冲的时间展宽从而降低焦斑峰值功率密度; 利用3TW钛宝石飞秒激光系统, 通过f/1离轴90°抛物面镜对激光束进行紧聚焦, 得到最佳焦斑尺寸为5.6μm×5.4μm, 对应于3mJ和96mJ的飞秒脉冲激光光束的焦斑峰值功率密度分别为3.83×1017W/cm2和1.23×1019W/cm2。结果表明, 该研究为开展激光与固体、气体、团簇等物质相互作用的相关实验提供了重要的参考。
激光光学 峰值功率密度 超短激光脉冲紧聚焦 离轴抛物面镜 laser optics peak power density focal spot of ultra-short laser pulse off-axis parabolic mirror
