激光熔覆参数对灰铸铁激光熔覆层裂纹的影响

通过调整激光熔覆工艺参数 ,对灰铸铁激光熔覆层裂纹问题的研究 ,发现表层裂纹率随激光扫描速度或激光功率的增加有最低值。结合激光熔覆工艺参数 ,分析了残余拉伸应力的变化 ,熔覆层树状晶的结晶方向及渗碳体组织长度和粗细程度的改变 ,同时也分析了珠光体的形态及分布与离异共晶的有无 ,解析了不同激光熔覆工艺参数形成不同裂纹率的原因。     

非晶硅薄膜的YAG激光晶化工艺研究

应用YAG激光器在不同工艺条件(激光脉冲频率及脉宽)下对非晶硅薄膜进行了微晶化处理。采用XRD和AFM对所制薄膜的物相结构和表面形貌进行了分析,并探索了激光脉冲占空比对非晶硅薄膜晶化的影响。结果表明,非晶硅薄膜在不同激光脉冲占空比情况下的结晶变化趋势均为多晶硅衬底表层先非晶化,后与非晶硅薄膜一起结晶,而利于其结晶的最佳占空比为1/25。已晶化硅薄膜的晶粒尺寸随占空比的增加先变大后变小。     

脉冲激光LGA法钛表面氮化及其XRD和SEM微观分析

用调Ｑ－ＹＡＧ和ＸｅＣｌ脉冲激光在钛表面以激光气体合金化方法生成氮化钛层，用Ｘ射线衍射仪分析了不同激光能量、不同Ｎ２气压不同作用脉冲数等条件下ＴｉＮ的结晶取向、结晶形态、氮化程度，用扫描电镜观察了它们的微观结构，对脉冲激光的ＬＧＡ法机理进行了探讨，也发现了用ＬＧＡ法对Ｍｏ的氮化生成Ｍｏ２Ｎ．     

激光脉冲冷冻水

低于正常冰点却没有结晶的液体称为过冷液体。利用声空穴过程，超声波可以在内部产生气泡，气泡破裂时产生晶核，使过冷液体结晶。欧洲科学家在研究声结晶机理时，用激光代替声波，把激光脉冲聚焦于液体中某一点，成功将过冷水结晶成冰。该技术将对材料和晶体生长有重大影响。     

氢化非晶硅液相激光结晶

用低速扫描对a-Si:H进行激光结晶,适当调整扫描速度、激光功率和光斑内能量分布,可以得到液相激光结晶(LP-LCR),晶粒尺寸可达20～30μm.重叠扫描可获得大面积的大晶粒多晶硅膜,有可能为器件制备提供一种薄膜材料.     

超快激光调控晶体形核与生长过程研究进展

物质的结晶在生物制药、大分子结构分析等领域有着重要的应用,这些应用对结晶结果(包括晶体数量、大小、晶型等)提出了一定的需求,而通过蒸发溶剂或改变温度使溶质析出结晶的传统方法,存在结晶结果难以控制的问题。近年来,超快激光在调控晶体形核生长中的应用得到了关注和研究。超快激光以其超快、超强的特点,在调控晶体形核与生长方面具有独特的作用,且具有热影响区域小、适用材料范围广等优势。本文综述了超快激光调控晶体形核生长过程的研究进展,主要包括超快激光诱导结晶形核、控制晶体生长过程以及晶面图案化加工三个方面,并对超快激光调控晶体形核生长研究的应用前景进行了展望。     

激光结晶a-Si:H SOI离子注入和快速退火

本文对激光结晶a-Si∶H SOI结构砷注入和快速退火行为作了研究.a-Si∶H激光结晶有Lp-LCR,OD,FCR-2,FCR-1四个结晶区.用剖面电镜观察了结晶区的结构.扩展电阻测量表明Lp-LCR区中有两种扩散机制,即杂质在晶粒体内扩散和沿缺陷扩散.OD区中有三种扩散形式,除有上述两种以外,还有沿缺陷的扩散.首次比较了沿晶界和缺陷的扩散速度.     

激光特性参数与激光生物效应

本文从国内近年来开展的多种激光生物效应实践出发,探讨激光特性参数对激光生物效应的影响。文中指出不同波长激光可对同一生物体产生同一类型变异,不同种类生物体对应最佳波长、最佳剂量不同。低剂量激光对众多生物体产生有效刺激效应。在低功率激光生物效应中空间相干性起主要作用。非偏振激光可获有效生物效应。文中还对某些实验现象作了解释。     

掺钕的玻璃陶瓷激光材料

本文叙述了首次报导的透明玻璃陶瓷激光基质。重要的是这是一种包含各向异性的结晶相和各向同性的玻璃相的双相材料。玻璃陶瓷基质具有激光材料所希望的某些物理性质,例如很低的热膨胀系数。玻璃或者玻璃     

金绿宝石激光晶体性能的研究

金绿宝石的结构为正光性双光轴晶体，从光谱分析激光特性；可产生宽带发射的激光跃迁，晶体的激光可使磷酸二氘钾进行倍频，BeAL2O4晶体中光沿三个结晶轴的每一个轴偏振。     

YAG激光和CO2激光相变硬化机理研究

研究YAG激光和CO2激光对金属热作用机理,建立了这两种激光对金属材料热作用的物理模型,并就所建立的物理模型进行了深入的理论和实验研究,验证了所建立的物理模型的正确性.     

1kW无氦横流连续CO_2激光器的研究

本文报道我们研制的 Ikw无 He横流连续CO_2激光器的实验结果。激光器总体结构如图1所示。其放电装置采用针板放电结构，阴极由152根直径为      

强CO_2激光辐照下离子注入Si反射率的动态干涉效应

本文从理论和实验研究了连续CO_2激光辐照下磷离子注入Si对He-Ne激光束反射率呈现的动态干涉效应。从反射强度随时间的变化看出,Si片离子注入层固相外延的速率在整个再结晶过程中是不均匀的。     

Experimental investigation of an optically pumped mid-infraredcarbon monoxide laser

Results from a dual experimental/theoretical investigation of an optically pumped room-temperature carbon monoxide (CO) laser are discussed. Ro-vibrational transitions in the (2, 0) overtone of CO at 2.3 μm were pumped with an optical parametric oscillator to generate lasing on (2, 1) band transitions near 4.7 μm. During the build-up of the laser pulse, only rotational redistribution of the initial optically pumped population was observed in the resolved CO spectra. Calculations describing the CO laser pulse dynamics and collisional relaxation rates support this observation. The addition of helium and argon bath gases enhanced the rotational relaxation process. A pressure dependent loss mechanism that degrades optical efficiency has been identified and possible causes are discussed     

On the excitation mechanism of the oxygen laser in a fast plasmamixing device

A flowing hollow cathode rare gas plasma crossed with an oxygen (O ₂) beam was used to operate an atomic oxygen laser at 8446.7 Å. Laser action based on energy transfer collisions was accomplished only with pure helium plasmas. With additions of 0.2% neon or 0.1% argon to the helium plasma, the laser ceased to operate and fluorescence was reduced. No fluorescence was observed if other O donors such as CO, CO₂, or N₂O were used. The excitation mechanisms for different O donor and rare gas combinations and different excitation methods are discussed     

Acoustic waves and heating due to molecular energy transfer in an electric discharge CO laser

This paper summarizes analytical studies and the interpretation of experimental results for the compression and rarefaction waves generated in the cavity of a pulsed CO electric discharge laser. A one-dimensional analysis of acoustic waves is applied to a transversely excited laser. The influences of heating in the cathode fall, heat transfer to the cathode, flow through both the anode and cathode, and bulk heating of the plasma are included. The analysis is used to relate the bulk heating rate to observable features of the pressure and density waves. Data obtained from interferograms and reported elsewhere are used to infer the bulk heating rates in a pulsed CO laser. Results are presented for CO/Ar, CO/N2, and N2plasmas. Comparison of the data with recent theoretical results for the heating due to electron/ neutral collisions and the anharmonic defect associated withV-Venergy transfer shows substantial differences at lower values of total energy deposition. The change of heating WithE/Nis in fairly good agreement with predicted values.     

脉冲激光能量的准确测量

本文介绍一种补偿锥腔量热计，进行了脉冲激光能量的准确测量，并对电脉冲和激光脉冲情况下的动态非等效性进行了研究。量热计辐射（能量）灵敏度的总的不确定度为0.2％。使用光学快门和稳定的连续氩离子激光时，比对量热计和绝对辐射（功率）计，两种标度符合0．05％以内。     

Measurements of a mode-competition discriminant in a single-frequency argon ion ring laser

We have built a single-frequency argon ion ring laser using a coupled-cavity mode selector. Utilizing the gain asymmetry caused by the drift velocity imparted to the argon ions by the dc field used to excite the discharge, we have obtained a narrow discriminant centered on the argon laser line. This discriminant could be used to stabilize the laser to the center of the atomic line. We have measured discriminant widths of less than 200 MHz for the argon 4880-Å resonance line. The sensitivity of this discriminant is compared with other laser stabilization systems described in the literature, and it is shown that our system appears to be the most sensitive of the systems currently available for stabilizing the argon ion laser.     

A high-performance polysilicon thin-film transistor using XeClexcimer laser crystallization of pre-patterned amorphous Si films

A high-performance polysilicon thin-film transistor (TFT) fabricated using XeCl excimer laser crystallization of pre-patterned amorphous Si films is presented. The enhanced TFT performance over previous reported results is attributed to pre-patterning before laser crystallization leading to enhanced lateral grain growth. Device performance has been systematically investigated as a function of the laser energy density, the repetition rate, and the number of laser shots. Under the optimal laser energy density, poly-Si TFT's fabricated using a simple low- temperature (⩽600°C) process have field-effect mobilities of 91 cm²/V·s (electrons) and 55 cm²/V·s (holes), and ON/OFF current ratios over 10 ⁷ at V_Ds=10 V. The excellent overall TFT performance is achieved without substrate heating during laser crystallization and without hydrogenation. The results also show that poly-Si TFT performance is not sensitive to the laser repetition rate and the number of laser shots above 10     

辅助气体对CO_2激光焊接光致等离子体屏蔽的影响

采用２０ｋＷＣＯ２激光加工系统焊接低碳钢，研究了辅助气体对等离子体屏蔽临界功率密度的影响。研究结果表明，辅助气体不同时等离子体屏蔽临界功率密度由小到大的排列顺序为：Ａｒ→Ｎ２→ＣＯ２→Ｈｅ。Ａｒ作为辅助气体时，等离子体屏蔽的临界功率密度可以低至１．８５×１０６Ｗ／ｃｍ２。辅助气体对等离子体屏蔽临界功率密度的影响主要取决于气体的导热性和解离能，相比而言，气体电离能的影响是次要的。采用Ａｒ作为辅助气体时，等离子体屏蔽临界功率密度低的原因主要在于Ａｒ的导热性能差，激光支持的燃烧波（Ｌａｓｅｒ－ｓｕｐｐｏｒｔｅｄＣｏｍｂｕｓｔｉｏｎＷａｖｅｓ—ＬＳＣ）波容易过热和扩展。