熔石英再沉积层结构的纳米级表征和杂质分析

利用原子力显微镜观察熔石英不同蚀刻时间的表面形貌,结合二次离子质谱分析,研究了熔石英的再沉积层结构和杂质分布。结果表明,熔石英表面深度10nm的再沉积层内存在大量微裂纹和杂质,经蚀刻展开形成nm级划痕和坑点,其分布随着深度增加呈指数衰减。根据nm级划痕密度、宽深比随蚀刻深度变化的规律,估算出再沉积层厚度,估算结果与二次离子质谱测得的杂质嵌入深度基本一致。杂质元素嵌入深度与抛光微裂纹分布特征的关联性表明,杂质很有可能藏匿在抛光微裂纹中。     

囚禁离子的非线性Jaynes-Cummings模型及其布居数反转演化

从描述囚禁离子与驻波激光场相互作用的Jaynes-Cummings(J-C)模型出发，导出了囚禁离子谐振动单量子共振激发相互作用的非线性J-C模型. 通过求解这一模型的系统状态随时间变化，数值研究了离子布居数反转的演化规律. 结果表明，离子布居数反转演化的崩塌-复原周期与Lamb-Dick参数η和离子在驻波激光场中的位置有关，随着η参数的增大，离子布居数反转的崩塌-复原周期变短，当离子质心的位置从驻波激光场的波节移向波腹时，离子布居数崩塌-复原的周期变长. 关键词： 驻波激光场 囚禁离子 非线性J-C模型 Lamb-Dick参数     

K9基片的亚表面损伤探测及化学腐蚀处理技术研究

 研究了几种类型的腐蚀液对K9基片化学腐蚀的影响。通过腐蚀液对基片纵向腐蚀速度的变化初步判断了K9基片重沉积层的深度。考察了腐蚀前后基片表面参数的变化以及腐蚀对激光损伤阈值的影响。研究表明,特定的腐蚀液能够对K9基片进行平稳可控的腐蚀,并且腐蚀能提高其激光损伤阈值,其主要原因是去除了重沉积层及表面、亚表面缺陷中的污染物,但过多的腐蚀会暴露本来为重沉积层所掩盖的划痕等亚表面缺陷,所以腐蚀并非越深越好。同时,表面各种杂质与缺陷的去除能够提高材料的机械强度,从而也有利于提高材料的激光损伤阈值。     

超短脉冲激光在电介质材料中传输及破坏深度微观理论计算

基于Fokker-Planck方程和激光传输方程建立超短脉冲激光在电介质材料中的传输及材料破坏理论模型,计算材料内不同位置处导带电子数密度及激光电场强度随时间的变化,进而得到激光的反射率、透射率及沉积率随激光能量密度的变化特征.选取导带电子数密度阈值作为材料破坏的判断条件,计算了不同激光能量密度下的破坏深度,发现破坏深度随激光能量密度的变化曲线呈现先增长后减小,讨论了激光能量沉积特性对破坏深度的影响.计算最大破坏深度随激光脉宽的变化发现,激光脉宽越短则最大破坏深度越小. 关键词： 超短脉冲激光 电介质材料 破坏深度 微观理论模型     

分子束外延PbTe单晶薄膜的反常拉曼光谱研究

采用分子束外延(MBE)方法在BaF₂(111)衬底上生长了高质量的PbTe单晶薄膜， 拉曼光谱测量观察到了表面氧化物的振动模、布里渊区中心(q≈0)纵光学(LO)声子振动模以 及声子-等离子激元耦合模振动.随着显微拉曼光谱仪激光光斑聚焦深度的改变，各拉曼散射 峰的峰位、积分强度、半高宽等都表现出不同的变化趋势. 随着激光光斑聚焦位置从样品表 面上方3μm处变化到表面下方3μm处，PbTe外延薄膜的LO声子频率从119cm^-1移 动到124cm^{-1关键词： PbTe外延薄膜 拉曼散射 纵光学声子}     

脉冲激光烧蚀中电声弛豫时间的确定

为了提高脉冲激光制备薄膜的质量,准确掌握电声弛豫时间是关键,它对脉冲激光脉宽和能量密度的选取起着决定性的作用. 文中以铝靶材为例,利用经典的双温方程通过时域有限差分法(FDTD)得到电子、离子亚系统的温度随时间和位置演化的图像,进而得到电声弛豫时间的准确值. 这样便能准确划分热烧蚀和非平衡烧蚀,从而更好地控制激光的烧蚀过程. 同时找出了电声弛豫时间随激光脉宽以及能量密度变化的规律. 关键词： 飞秒激光 电声弛豫时间 双温方程 激光能量密度     

激光处理样品的辉光放电发射光谱表面逐层分析

应用辉光放电发射光谱(GD-OES)对经过激光处理的材料进行了表面逐层分析,深度达371μm,得到了所有5种合金元素Fe、Cr、Ni、B和Si的含量随深度变化的分布曲线。     

皮秒激光烧蚀Al膜的理论分析与实验验证

为研究Al膜受短脉冲激光作用时的能量传输过程,建立了一维半经典双温热传导模型。根据材料加工过程的熔化现象,对模型的相变区域进行有效设置。通过有限元法求解,得到晶格温度随时间分布的规律。根据自由电子气理论优化了模型,得到Al膜表面反射率和热吸收系数随时间的分布图。得到了激光辐照所产生热电场的分布规律,并分析了电子温度梯度对其影响。描绘出电子漂移运动速度的分布规律,证实激光作用产生的热电场是电子漂移运动的主导因素,发现最大漂移速度位置随时间的延长而加深。对激光作用后的晶格温度进行了区域性分析,定义了过热加热区,并得到激光烧蚀深度随时间的变化关系。实验结果表明,不同功率皮秒激光烧蚀Al膜的深度接近于理论计算结果。     

Al和C8H8的激光烧蚀深度测量

 叙述了采用时间积分的晶体谱仪探测不同发次衬底元素离子谱线强度的相对变化外推激光烧蚀深度的方法，获取了Al和C₈H₈的激光烧蚀深度，进而推出了Al和C₈H₈的质量烧蚀速率和烧蚀压。对实验结果进行了分析和讨论。     

飞秒双脉冲激光照射金属薄膜的热行为

通过双温方程对飞秒单脉冲与双脉冲照射金薄膜进行了计算模拟分析,得到了金靶的电子温度和晶格温度随着时间空间的变化。在同样激光能量密度下,单脉冲与双脉冲使得金膜温度的变化表明双脉冲使得更多的激光能量渗透到靶材内部,这些能量可以使得烧蚀深度更深,有利于提高激光烧蚀靶材的效率。计算结果显示随着激光能量密度的增加熔化面深度逐渐增加,单脉冲与双脉冲熔化面深度的变化明显不同。在激光能量密度高于损伤阈值附近,单脉冲的烧蚀深度大于双脉冲的烧蚀深度,随着激光能量密度增加,双脉冲的烧蚀深度将大于单脉冲的烧蚀深度。     

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介绍了用于保护HL-2A装置远红外激光干涉仪探测器的双色滤波器。根据双色滤波器理论优化设计了双色滤波器的外型和结构,并首次用于HL-2A远红外激光干涉仪密度测量系统。实验结果表明,当双色滤波器长度l=0.2mm,直径d=0.23mm,孔之间的间隔s=0.33mm时,双色滤波器能够很好地隔离68GHz的ECRH波带来的干扰,并对890GHz的HCN激光波有较好的透过率。     

双色滤波器在远红外激光干涉仪上的应用

介绍了用于保护HL-2A装置远红外激光干涉仪探测器的双色滤波器。根据双色滤波器理论优化设计了双色滤波器的外型和结构,并首次用于HL-2A远红外激光干涉仪密度测量系统。实验结果表明,当双色滤波器长度l=0.2mm,直径d=0.23mm,孔之间的间隔s=0.33mm时,双色滤波器能够很好地隔离68GHz的ECRH波带来的干扰,并对890GHz的HCN激光波有较好的透过率。     

Laser cutting of thick ceramic tile

This paper details developments in the CO₂ laser cutting of thick ceramic tiles, that is thicknesses of 8.5 mm and 9.2 mm. These tiles were cut at a combination of different cutting speeds to determine the necessary cutting parameters for various tile geometries. Different cutting modes were used in conjunction with different cutting speeds to investigate cut quality after laser processing. The work also looked into the effects on cutting through using various shield gases. Multipass cutting and underwater cutting were performed to examine their effects on thermal load during processing.     

CO2 laser cutting of slate

Slate is a natural stone which has the characteristic that shows a well-developed defoliation plane, allowing to easily split it in plates parallel to that plane which are particularly used as tiles for roof building. At present, the manufacturing of slate is mostly manual, being noisy, powdery and unsafe for the worker. Thus, there is a need to introduce new processing methods in order to improve both the working conditions and the quality of the products made of slate.Following the previous work focused on the drilling and cutting of slate tiles using a Nd : YAG laser, we present in this paper the results of the work carried out to explore the possibilities to cut slate plates by using a CO₂ laser. A 1.5 kW CO₂ laser was used to perform different experiments in which, the influence of some processing parameters (average power, assist gas pressure) on the geometry and quality of the cut was studied. The results obtained show that the CO₂ laser is a feasible tool for a successful cutting of slate.     

Film growth and mechanism of LICVD of chromium films from Cr(CO)6 at 248 nm

The probe-beam transmission method was used to study the chemical vapor deposition of chromium films due to photodecomposition of Cr(CO)₆ by pulsed excimer laser radiation at 248 nm in a reversed-substrate configuration, where the film forms on the quartz entrance window of the deposition cell. The dependence of the deposition rate and the film formation time on the laser pulse intensity and repetition rate as well as on the Ar buffer gas pressure was determined for different stages of the deposition process. The experiments were performed at room temperature, on a deposition area of about 0.15 cm², with laser fluences up to 100mJ cm^–2, pulse repetition rates between 5 and 80 pps and buffer gas pressures between 10 and 700 mbar. The results are discussed within the framework of a simple model for LICVD. They reveal the dominant role of gas-phase photodissociation and diffusion in chromium film deposition under the conditions employed. Some results concerning the morphology and the depth distribution of Cr, O, and C in films deposited in the reversed-substrate configuration are also presented.     

The Progression of the Impurities Injected into the Plasma Following by Soft X-ray Arrays on HL-2A Tokamak

Small amounts of metallic impurity is injected by laser blow-off on HL-2A tokamak in order to study transport phenomena. The particle transport is interpretated along     

HL-2A装置YAG激光汤姆逊散射测量电子温度的初步结果

 叙述了激光汤姆逊散射的实验原理,介绍了HL-2A装置上改进后的激光汤姆逊散射系统。高脉冲功率Nd：YAG激光光源发出的1 064 nm的激光能很好地满足测量等离子体电子散射光的要求,硅雪崩光电二极管和窄带干涉滤波片组成的多色仪的使用,大大提高了散射光的测量效率。数据处理方法采用按测量误差进行权重分析的查表法,提高了数据处理的速度。最后介绍了各种放电条件下的单空间点电子温度的测量结果。     

A melt depth prediction model for quality control of laser surface glazing of inhomogeneous materials

This paper reports on an investigation into the development of an analytical model for the quality control of laser marking/engraving of clay tiles using a high-power diode laser (HPDL). An analytical model for the laser melting of inhomogeneous workpieces with parabolic melt pool geometry being assumed was developed. The theoretical results were compared with the experimental data. The predicted melt pool depth and the experimental values were in close correlation with the parameter for values less than 15 Wmm⁻¹ s^−1/2, in spite of simplifications introduced in the model. At the relatively large values of parameter the assumption of parabolic melt pool shape and one-dimensional heat transfer no longer holds true.     

HL-2M 装置限制器系统设计及工艺研究

HL-2M 装置设计有 8 套固定极向限制器和 1 套活动极向限制器,其主要功能是进一步加强保护真空 室及其内部件,同时活动限制器还将提供不同孔栏位形用于等离子体物理实验。根据 HL-2M 装置总体运行需求, 活动限制器结构设计可移动有效距离为 120mm,活动限制器移动精度可控制在±0.1mm 以内。基于激光跟踪仪测 量方法对 HL-2M 装置限制器系统完成了高精度的安装,限制器的面向等离子体关键位置安装精度优于±0.5mm, 通过初始等离子体放电实验表明其运行状态均正常。