脉冲激光束质量的同步测量

研究评价脉冲激光束质量的同步测量方法,方法通过分析脉冲激光光束和ＣＣＤ测量系统的特点,提出在低重复和高重复频率情况下的多种同步测量方法,并通过对钇铝石榴石激光光束质量的评价实验加以验证。结果成功地不同脉冲频率下对ＹＡＧ脉冲激光光束质量进行了评价,并计算出光束质量因子的数量级为１０。     

kHz 脉冲分子束的产生及其在强场原子分子物理实验中的应用

采用悬臂压电脉冲阀, 制备出最高重复频率达到3 kHz 的脉冲分子束。通过测量氮气分子束在飞秒激光作用下隧道电离生成的N2 +(B-X)荧光光谱, 对脉冲阀的性能做了表征。这种kHz 脉冲分子束搭配kHz 飞秒激光器, 将推动飞秒强激光驱动的原子分子动力学实验研究。     

应用粒子成像测速技术测量压力振荡器的瞬态流场

利用以两台大功率脉冲激光器为双脉冲光源的粒子成像测速 (PIV)技术 ,测定了驻波管型正弦压力振荡器二维振荡射流瞬态流场 ,对示踪粒子的跟随性进行了比较 ,分析了示踪粒子在流场中的浓度分布对成像质量的影响。实验结果表明 ,环形喷嘴射流与尖劈之间存在交错的、方向相反的旋涡是使整个系统产生流体自激振荡的原因 ,环形喷嘴与尖劈之间的距离对瞬态流场有明显的影响。由双脉冲激光作光源的PIV系统具有脉冲间隔调节范围宽、测量精度高等特点 ,非常适合于从低速到高速全范围的流场测量     

硅酸盐玻璃YAG激光损伤研究

测量了硅酸盐玻璃的ＹＡＧ激光损伤阈值，以及重复频率脉冲的积累效应，并研究了光学材料中的非线性吸收过程。分别采用了ＣＷＣＯ２激光预辐射和恒温预烘烤方法来研究如何提高光学的激光损伤阈值问题，并简要分析了相关的机理。     

小型脉冲工作的光泵CH3OH分子远红外激光器

小型脉冲工作的光泵ＣＨ３ＯＨ分子远红外激光器黄晓秦家银郑兴世（中山大学无线电电子学系，广州５１０２７５）关键词ＣＨ３ＯＨ，远红外激光，脉冲光泵激光分类号Ｏ４３３．５４ＣＨ３ＯＨ（甲醇）是最常用的远红外激光工作物质之一，迄今已从ＣＨ３ＯＨ中产生了５７...     

柴油机冲突喷雾的可视化和浓度测量研究

围绕激光ＣＴ技术在柴油机喷雾测试上的应用进行研究，开发了一套柴油机喷雾的激光ＣＴ测试系统．应用脉冲激光和ＣＣＤ摄象机的特性，将柴油机喷雾图象实时采集到计算机图象处理系统上．最后，对１３５柴油机喷嘴的冲突喷雾进行了测量，用ＡＲＴ重建了三维喷雾图象，实现了燃油喷雾内部构造的可视化和三维相对浓度分布的测量．     

强场原子分子物理实验研究中的符合测量技术及其应用

飞秒激光具有超短的脉冲宽度和超强的峰值功率，已经成为测量和操控原子分子超快动力学行为的重要工具．但是强激光场下，原子分子行为非常复杂，多个反应通道纠缠在一起．全微分符合测量技术能够提供特定反应通道精确的动力学数据，推动了强场原子分子物理研究的快速发展．本文结合北京大学新建的冷靶反冲离子动量谱仪，介绍全微分符合测量技术在强场原子分子物理实验研究中的重要应用以及在强场原子分子物理实验研究方面取得的一些重要进展．     

二束脉冲激光提高CO2分子取向的温度效应

借助于分子刚性转子模型,利用数值方法求解了CO2分子在二束脉冲激光作用下的薛定谔方程,计算了CO2分子在总强度I=1.0×1014W/cm2固定激光脉冲作用下分子取向的变化行为。研究结果表明,在不同温度下当激光总强度固定时,将一束激光脉冲分成具有同样脉冲宽度的二束脉冲,当强度比为1/3时,都可以极大地提高CO2分子的取向程度;在不同温度下,通过调整第2束脉冲宽度,可以进一步提高CO2分子的取向程度。以上结果对实验中在不同温度下提高分子取向具有指导意义。     

应用粒子成像测速技术测量压力振荡器的瞬态流场

利用以两台大功率脉冲激光器为双脉冲光源的粒子成像测速（ＰＩＶ）技术,测定了驻这型正统压力振荡器二维振荡射流瞬态流场,对示踪粒子的跟随性进行了比较,分析了示踪粒子在流场中的浓度分布对成像质量的影响。实验结果表明,环形喷嘴射流与尖劈之间存在交错的、方向相以的旋涡是使整个系统产生流体自激振荡的原因,环形喷嘴与尖劈之间的距离对瞬态流场有明显的影响。由双脉冲激光作光源的ＰＩＶ系统具有肪冲间隔调节范围宽、测量     

二束飞秒脉冲对O_2分子转动波包的适时控制

为了确定最佳延迟时间,更加有效控制分子转动波包。通过数值求解O2分子在脉冲激光作用下的薛定谔方程,研究了O2分子在飞秒激光作用下的转动波包特征。计算结果表明,在分子转动波包的第1个恢复周期附近,根据取向参数变化率,加上具有恰当延迟时间的第2束激光脉冲,能极大地提高分子取向,从而改变波包的转动特征;同样,在分子转动波包的二分之一恢复周期附近,根据取向参数变化率,加上具有恰当延迟时间的第2束激光脉冲,能极大地降低分子取向,从而有效抑制分子转动波包。在激光强度不变的情况下,只要同时改变二束激光的脉冲宽度,适时控制延迟时间,能进一步提高分子取向,从而有效控制分子转动波包。     

催化共振散射光谱法测定木瓜蛋白酶活力

木瓜蛋白酶催化水解酪蛋白生成小分子氨基酸和肽,剩余底物酪蛋白与三氯乙酸结合形成粒径约为1740nm的缔合物微粒。该微粒在360、400、420、470、520nm处产生5个共振散射峰,其中最强峰位于470nm。在选定条件下,随着木瓜蛋白酶量的增加,体系中剩余酪蛋白浓度降低,470nm处的共振散射光强度,Ⅰ470nm降低。木瓜蛋白酶的酶活力在0．024～4．8 USP／mL范围内与470nm处的共振散射光强度降低值△Ⅰ470nm呈现良好线性关系,检出限为0．0083 USP／mL。该共振散射光谱法用于嫩肉粉中木瓜蛋白酶活力测定,结果满意。     

Clathrate nanostructures for mass spectrometry

The ability of mass spectrometry to generate intact biomolecular ions efficiently in the gas phase has led to its widespread application in metabolomics, proteomics, biological imaging, biomarker discovery and clinical assays (namely neonatal screens). Matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization have been at the forefront of these developments. However, matrix application complicates the use of MALDI for cellular, tissue, biofluid and microarray analysis and can limit the spatial resolution because of the matrix crystal size (typically more than 10 mum), sensitivity and detection of small compounds (less than 500 Da). Secondary-ion mass spectrometry has extremely high lateral resolution (100 nm) and has found biological applications although the energetic desorption/ionization is a limitation owing to molecular fragmentation. Here we introduce nanostructure-initiator mass spectrometry (NIMS), a tool for spatially defined mass analysis. NIMS uses 'initiator' molecules trapped in nanostructured surfaces or 'clathrates' to release and ionize intact molecules adsorbed on the surface. This surface responds to both ion and laser irradiation. The lateral resolution (ion-NIMS about 150 nm), sensitivity, matrix-free and reduced fragmentation of NIMS allows direct characterization of peptide microarrays, direct mass analysis of single cells, tissue imaging, and direct characterization of blood and urine.     

Resistless photochemical etching of a silicon wafer by UV laser with an H2O2 and HF aqueous solution

A new resistless etching method has been developed for Silicon wafers. This new method uses an aqueous solution consisting of hydrogen peroxide (H2O2) and hydrogen fluoride (HF) as the activating etchants. A 193 nm ArF excimer laser and a 266 nm fourth harmonic generation Nd:YAG laser were used as the photon sources. Results showed that pattern etching has been achieved without any photoresist film. In the case of the 193 nm laser, the optimal etching appeared at a 1.3 H2O2/HF ratio, where an etch depth of 210 nm was achieved with a fluence of 29 mJ/cm2 and shot number of 10000. At the same conditions, the etch depth with H2O2 and HF solution was three times of that by using H2O and HF mixture. In the case of the 266 nm Nd:YAG laser, the optimal etching appeared at twice ratio of H2O2/HF, where the etch depth of 420 nm was achieved with a fluence of 12 mJ/cm2 and shot number of 30000. Results showed that the etch effect of the 266 nm Nd: YAG laser was more desirable than that of the 193 nm ArF excimer laser.``Keyords: UV laser, resistless photochemical etching, hydrogen peroxide (H2O2).     

Resistless photochemical etching of a silicon wafer by UV laser with an H<Superscript>2</Superscript>O<Superscript>2</Superscript> and HF aqueous solution

A new resistless etching method has been developed for Silicon wafers. This new method uses an aqueous solution consisting of hydrogen peroxide (H₂O₂) and hydrogen fluoride (HF) as the activating etchants. A 193 nm ArF excimer laser and a 266 nm fourth harmonic generation Nd: YAG laser were used as the photon sources. Results showed that pattern etching has been achieved without any photoresist film. In the case of the 193 nm laser, the optimal etching appeared at a 1.3 H₂O₂÷HF ratio, where an etch depth of 210 nm was achieved with a fluence of 29 mJ/cm² and shot number of 10000. At the same conditions, the etch depth with H₂O₂ and HF solution was three times of that by using H₂O and HF mixture. In the case of the 266 nm Nd: YAG laser, the optimal etching appeared at twice ratio of H₂O₂/HF, where the etch depth of 420 nm was achieved with a fluence of 12 mJ/cm² and shot number of 30000. Results showed that the etch effect of the 266 nm Nd: YAG laser was more desirable than that of the 193 nm ArF excimer laser.     

1319nm与660nm双波长Nd:YAG激光器的研究

为研究获得高功率红光的有效方法,研制了一种准连续输出1319nm与660nm双波长Nd:YAG激光器.文中分析了波长1319nm激光的辐射跃迁能级,论述了抑制1064nm激光的生成从而提高1319nm激光输出等关键技术,研究了光学镜片的镀膜参数与腔型结构,实现1319nm激光连续输出最高功率43W,以1319nm激光为基频,置入KTP晶体内腔倍频,并设置声光Q开关,获得660nm红光准连续输出2W,实现1319nm与660nm双波长输出.     

LiIO3晶体中和频产生连续355nm紫外光分析

在环形腔ＹＡＧ连续稳频激光器上，通过ＬｉＮｂＯ３晶体腔内倍频输出的１０６４ｎｍ和５３２ｎｍ的单频激光，在腔外聚焦到ＬｉＬＯ２晶体中和频产生了３５５ｎｍ的紫外光。     

Covariance analysis of the Coulomb explosion of ammonia induced by intense nanosecond laser at 532 nm

The Coulomb explosion of ammonia clusters induced by nanosecond laser at 532 nm with an intensity of ～1012 Wcm^-2 has been studied by time of flight mass spectrometry. The dominant multiply charged ions are N^3＋ and N^2＋ with kinetic energies of 110 and 50 eV respectively. The electrons generated from the multiphoton ionization are heated through inverse bremsstrablung by tbe laser field when colliding with neutral or ionic particles. When their energies surpass the corresponding ionization potentials of the molecules or ions, the subsequent electron impact ionization may take place thus resulting in multi-charged nitrogen ions. Covariance analysis is made to study the possible pathways of the Coulomb explosion.     

双色激光激励对空气中太赫兹辐射增强的研究

利用光电流模型模拟研究在泵浦光中引入400nm倍频光对空气中太赫兹辐射的增强情况,其中空气中氮气离化过程考虑到二阶离化,同时考虑电子在运动过程中与周围离子、分子的碰撞。结果表明,400nm激光的引入打破了原激光电场的对称性,导致了光电流中漂移成分的产生,大大增强了最后的太赫兹波输出强度。     

水溶性聚苯胺/碳纳米管复合材料的制备及光限幅性能

为了制备激光防护材料,采用原位聚合法制备了水溶性聚苯胺/多壁碳纳米管复合材料。通过红外光谱分析、紫外-可见光光谱、透射电子显微镜等表征,用方形四探针法测量薄膜电导率。结果表明,水溶性聚苯胺包裹在碳纳米管表面,聚苯胺包裹层的厚度大约在15～25 nm;复合材料的薄膜电导率较水溶性聚苯胺的电导率提高了一个数量级。复合材料水分散液在低入射光强下透光率接近85%时;入射光强达到2.5 J/cm2,透光率降至11%。因此,复合材料水分散液的光限幅性能优于碳纳米管,具有良好水分散性,有望实现材料的器件化。     

外腔半导体激光器的实验研究

本文报道了外腔半导体激光器的一些研究成果。利用闪耀光栅作反馈元件，对808nm波长的半导体激光器形成弱耦合外腔，实现了光谱特笥较好的窄线宽单模激光输出，线宽小于0.06nm，边模抑制比大于30dB，最大输出功率为35.4mW，总的光－光转换效率为46％。通过调整光栅转角，可以得到11.66nm的波长调谐范围。设计了光栅－反向镜联动结构，使外腔半导体激光器的输出方向不再随调谐而变化。