超快激光在纳米溶液中的超连续光丝光谱技术

为了产生宽谱带超连续白光光谱,将飞秒激光聚焦到纳米溶液中形成光丝,最终产生出400～950 nm的超连续白光光谱。采用集成CCD的显微镜装置对伴随光丝的气泡进行拍摄,并研究了气泡定向运动的规律。计算表明,气泡的运动速度可以达到0.16 m/s,这表明水流也可以达到相应的速度。这种由光丝导致的高速水流,可对微流控技术的研究起到积极的作用。     

多丝切割机走丝系统的张力控制

多丝切割是一种新兴的硅片切片加工方法,在硅片的多丝切割加工中,金属丝的张力控制是影响加工的重要因素,本文分析了多丝切割机走丝系统的特点,采用张力控制电机实现走丝系统的速度差张力控制。仿真结果表明该方法可以满足走丝系统张力控制的高精度、高响应速度、波动小的控制要求。     

快走丝线切割机床断丝现象分析及解决方法探微

快走丝线切割机床是我国电加工行业中对模具进行加工的主要设备。在加工行业中应用较广。快走丝线切割机床比慢走丝线切割机床具有更高的性价比,能够解决一般机器无法解决的难题。但是在其工作过程中很容易断丝,这会严重影响模具的性能,对工作效率也会造成严重威胁。本文主要对快走丝线切割机床断丝现象进行分析,以及结合实际提出解决的方案。     

快走丝线切割脉宽与间隙对加工质量影响分析

通过一系列的实验得出脉冲宽度或脉冲间隔与加工表面粗糙度、精度、机床型号的关系,总结出放电电路能量及电流脉冲宽度、脉冲间隔对线切割电火花精加工表面粗糙度的影响规律.在实际生产加工中,结合实际清况,选择合适的脉冲宽度、脉冲间隔比,调节出合适的加工速度,这样能有效地控制工件的表面粗糙度,提高加工效率.实验结论可为提高线切割加工质量找出一条新途径,也为今后高频电源的开发,加工技术的提高提供重要参考依据.     

快走丝线切割机床的工艺特点及断丝因素探析

从快走丝线切割机床加工工艺特点出发,简述了断丝杌理,分析了导致断丝的因素,并提出了相应的解决办法.     

超发光现象

美国能源部布鲁克海文国家实验室的研究小组日前采用新技术获得了超短光脉冲，并称该技术有望用于能捕捉分子和原子运动的新一代光源设备。在新出版的《物理评论快报》上，研究人员介绍说，他们在利用激光束控制自由电子激光光脉冲持续时间的实验中，首次观察到了超发光现象。[第一段]     

DK7732线切割快走丝机床的技术改进

针对DK7732线切割快走丝机床在加工较厚工件或者铝合金件时经常会出现的断丝现象,分析产生此种现象的原因并对机床进行改造.通过在机床前导轮中加入导电装置,可很好地改善机床的导电性,并取得了良好的效果.     

快走丝线切割断丝原因分析及对策

针对与快走丝线切割加工中经常会发生的断丝现象,从钼丝的选择、机床的机械部分、工作液、装夹工件、放电参数的选择等方面分析了断丝的原因,给出了减少断丝的措施,这些措施能切实有效地减少断丝现象发生.     

快走丝线切割新型夹具的设计与制作

针对多型腔类零件加工时装夹和找正定位精度不高,而专用夹具又价格昂贵的问题,设计并制作了易使用、易安装的夹具,在一定程度上解决装夹与找正过程中的精度问题。设计的夹具主要由一块36等分的分度盘和分度盘盘架以及分度盘固定零件组成。通过应用实验证明,用此夹具装夹多型腔类零件时,能有效地减少工件的装夹和定位时间,提高加工效率,同时该夹具能让快走丝线切割机床不仅局限于二维图形的加工,而且扩大了零件的装夹加工范围,因而具有广阔的应用市场前景。     

单色超快激光成丝产生太赫兹辐射机理

单色超快激光与气体介质相互作用成丝产生太赫兹波是当前产生宽频太赫兹辐射的一个重要途径。介绍了不同模型下单色场(波长为0.8μm)超快激光与气体介质作用产生宽频强太赫兹辐射的产生机制,以及提升太赫兹波产生效率的几种方法。单色激光与气体介质作用产生太赫兹辐射的产生机制模型有渡越-切仑科夫辐射模型、激光有质动力模型和轫致辐射模型。研究表明,在拉丝周围外加横向电压、外加纵向电压和双拉丝的方法都能获得更强的太赫兹波。     

Experimental diagnostic module for ultrafast combined interferometry of the processes of interaction of ultrashort laser pulses with condensed media in vacuum

An experimental diagnostic module based on a femtosecond laser system (τ_0.5 ∼ 45-70 fs, 7n = 266, 400, and 800 nm) and the experimental technique for ultrafast combined interferometric investigation of the interaction of ultrashort laser pulses with condensed media in vacuum are described. A combined interferometric microscope built according to the Michelson and Mach-Zehnder schemes allows studies of the dynamics of optico-thermophysical and gas-dynamic proc esses at the surface of a target (the crater depth and diameter, optical properties) and in a plasma plume (velocity of expanding particles, electron density, optical characteristics) at a time resolution of 5 - 10^-14 s in the range of delays 10^-13-10^-7 susing two probing wavelengths (7n = 400, 800 nm) in vacuum (to 5 - 10^-5 mbar). Setting a mechanical shutter in the reference arm of the interferometer also allows obtaining of shadow photographs without changing the optical scheme.     

ir laser induced fluorescence cell for multiple photon processes

An efficient, easy to construct, long-path laser-induced fluorescence cell is described which is useful in studies of multiple ir photon induced phenomena.     

紫外飞秒激光泵浦氮气离子相干辐射

氮气分子在不同波长（中红外、近红外、紫外）强场飞秒激光的泵浦下,其分子离子在传播前向能够发出具有良好相干性的可见光波段的窄带辐射。在400 nm紫外飞秒激光的激发下,波长为428 nm和423 nm的相干辐射受到的关注较少,物理性质尚不明确。本研究对该辐射的偏振性质、气压和泵浦激光能量依赖关系进行了系统的测量。实验发现,该辐射的偏振与线偏振泵浦激光的偏振态保持一致,辐射强度随着气压和泵浦激光能量呈现出非线性的增加。利用基于密度矩阵的强场电离和能级耦合模型,对氮气分子在强场中的电离和相关离子能级在强场作用下的耦合进行了数值模拟研究。结果表明,在较大的激光强度范围内,氮气离子上能级$ {\mathrm{B}}^{2}{\mathrm{\Sigma }}_{\mathrm{u}}^{+} $和其离子基态$ {\mathrm{X}}^{2}{\mathrm{\Sigma }}_{\mathrm{g}}^{+} $之间,对应428 nm和423 nm的振动态之间总是能够形成粒子数反转,而且该反转对于激光参数具有鲁棒性,与实验观测结果一致。     

Recast layer removal using ultrafast laser in titanium alloy

Recast layer, which has undesirable effects on the fatigue resistance and service life of components and microstructures, has been observed and analyzed from the points of surface morphology and internal microstructure by three test methods including scanning electron microscopy, metallographic corrosion analysis, and transmission electron microscopy in this study. In order to reduce the harms of these unwanted recast layers, taking ultrafast laser as a post-machining method for recast material removal is proposed based on the advantages of ultrafast laser micromachining technology, which include the wide material applicability and absence of the recast layer during processing. The feasibility of this new recast layer removal method was verified by experiments on Ti-6Al-4V. With a series of optimized processing parameters, horizontally bedded scanning processing was adopted ultimately in final recast layer removal experiment because of its higher material removal rate and better machined surface quality compared with vertically shifting scanning processing. Based on the theoretical analysis and experimental results, ultrafast laser could be widely applied in more fields of microstructures finish machining.     

纳秒、皮秒和飞秒激光脉冲对材料表面的改性

对基体材料镉镍铁合金600和多层TiAIN/TiN涂层的激光表面改性在基础研究和实际应用中有着很好的前景.本文观察了由超短脉冲(fs和ns)和短脉冲(ns)激光器引起的镉镍铁合金600和TiAIN/TiN镀层的表面变化.结果显示,3种激光都能使靶面发生形态改变,超短脉冲的破坏轮廓更为清晰.与Ps激光脉冲相比,fs激光脉...     

皮秒脉冲隐形切割碳化硅晶圆实验研究

为了实现高速度切割碳化硅（SiC）晶圆,采用自行研制的高能量皮秒脉冲光纤激光器进行了隐形切割实验。依据切片的截面形貌、表面热损伤区和边缘直线度,分析了皮秒激光器的切割结果,并探究了单脉冲能量和扫描速度对切片质量的影响。结果表明,当使用中心波长为1 030 nm、重复频率为100 kHz、单脉冲能量为20μJ、脉冲宽度约为100 ps的皮秒脉冲隐形切割360μm厚度的SiC晶圆时,切片的质量能够满足实际应用要求,且激光的扫描速度可达400 mm/s,相应的切割速度为44.44 mm/s,高于其他相关报道。     

Acousto-optic modulator system for femtosecond laser pulses

Femtosecond laser pulses have made a revolution in multiphoton excitation microscopy, micromachining, and optical storage for their unprecedented high peak power. However, modulation of their intensity with acousto-optic modulator (AOM) is frustrated by dispersion which results in a significant stretch in pulse width. Here we report a scheme composed of two acousto-optic deflectors (AODs) to modulate the intensity of the femtosecond laser pulses with simultaneous compensation for the temporal dispersion. With commercial AODs, we demonstrated such an AOM system for the femtosecond laser pulses with overall transmission efficiency of around 80%. The pulse width of the exit beam is 115-177 fs for an input pulse of 110 fs, across the wavelength range of 720-920 nm when the temporal dispersion compensation is optimally tuned at 800 nm. The fluorescence intensity in a two-photon microscopy experiment performed using this system increased 5.5-fold over that of the uncompensated AOM.