长脉冲Nd:YAG激光器驱动电源与控制技术

改进了适合于长脉冲激光器泵浦氪灯的驱动电源和控制技术,特别是在脉冲式预燃方式、放电脉冲时间的精确控制以及大幅度减小电源发热量(近一个数量级)等方面.完成的装置具有工作稳定、可靠、效率高、智能操作、控制方便等优点,可广泛应用于YAG型激光医疗设备和工业加工设备.     

Nd:YAG透明陶瓷的制备与激光输出

成功制备了高质量的Nd:YAG透明陶瓷, 激光测试样品的尺寸为3mm×3mm×3mm, 双面抛光、未镀膜, 最高连续输出能量为1003mW, 斜率效率为14%.     

稳功率Nd：YAG连续激光器

选用高频开关电源作Ｋｒ灯电源，并使用热稳谐振腔、特殊聚光腔等，使Ｎｄ：ＹＡＧ连续激光器输出功率的稳定度达到±２％的水平。     

Continuous Wave ND:YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys

A continuous wave 4 kW Nd:YAG laser system was used to weld 2-mm butt joints of sand-cast ZE41A-T5 magnesium alloys at a power of 2.5 kW, welding speed of 6.0 m/min, and defocusing distance from - 2 to + 3 mm for the material in the machined surface conditions. It was found that the adjustment of defocusing distance greatly influences the establishment of conduction or keyhole mode welding. Conduction welding is obtained at a power density of 4.0 × 10⁵ W/cm². Keyhole welding is reached at a threshold irradiance of 1.5 × 10⁶ W/cm². The fusion zone consists of refined equiaxed grains formed through cellular growth in the Zr-containing magnesium alloys. The partially melted zone is rather narrow, only a few grains wide. No grain growth or coarsening but softening is observed in the heat affected zone (HAZ). The weld defects observed include three main types: imperfect shape, cavities, and weld cracks. The mechanisms of their formations are discussed. In addition, the original cast quality was found to have a significant influence on the formation of defects such as underfill, surface depression, porosity, and burn-through during laser welding.     

Characterization of Platinum and Gold ions emitted from laser produced plasmas using solid state nuclear track detectors

Investigations on key characteristics of ions emitted from Laser Induced plasmas are reported. A Q-switched Nd: YAG pulsed laser at 1064 nm, 9-14 ns and 1.1 MW, is focused on 4 N pure Gold (Au) and Platinum (Pt) targets to produce plasma plume. The ions thus emitted are detected by CR-39 Solid State Nuclear Track Detectors (SSNTD’s), placed at angles 0°, 30°, 60°, and 90° with respect to the target normal. The distances between the targets and detectors are 9 cm. The experiments are performed under a vacuum ∼10⁻³ torr and the ion tracks are recorded on SSNTD’s for 300 laser shots. The etched detectors are analyzed with the help of Motic Images Optical Microscope (Motic Advance 3.1). The flux of ions exhibits anisotropic behavior where as maximum energies of these ions are not only anisotropic but also forward peaked.     

球磨转速对Nd:YAG透明陶瓷的显微结构及光学性能的影响

以高纯商业Y₂O₃、α-Al₂O₃和Nd₂O₃粉体为原料, 以TEOS(正硅酸乙酯)和MgO为烧结助剂, 采用固相反应和真空烧结技术制备了1.0at%Nd:YAG透明陶瓷。系统研究了球磨转速(球磨时间10 h)对混合粉体的尺寸以及对陶瓷样品致密化行为、显微结构和光学性能的影响。结果表明: 通过球磨过程可以充分细化原料粉体的颗粒; 随着球磨转速的提高, 陶瓷烧结时样品中的气孔能更好地排除。但是球磨转速过高时, 陶瓷烧结体中存在少量的富铝第二相会降低样品的光学透过率。当球磨转速为130 r/min时, 真空烧结(1760℃×50 h)所得Nd:YAG透明陶瓷的微结构均匀致密, 几乎没有晶界和晶内气孔存在, 样品在1064 nm处的直线透过率高达83%。     

Properties of ITO on plastics and glass by Nd:YAG laser deposition at 355 and 532 nm

Indium tin oxide (ITO) was deposited on polycarbonate (PC), polyethylene terephthalate (PET) and glass substrates at room temperature and in a low-pressure oxygen environment by a pulsed Nd:YAG laser at 355 and 532 nm. The ITO film resistivity varied with the oxygen pressure, which achieved the lowest value of 1.5 × 10⁻³ Ω cm from the four-point probe measurements. The highest optical transmittance which depended on the target-to-substrate distance, was determined from UV-vis-NIR spectrophotometer. The highest optical transmission was 94% at 5 cm. The carrier concentration, of the order of 10¹⁹ cm⁻³ was determined from the Hall-effect measurements. Those films deposited at 355 nm of laser wavelength did show some better properties as compared to 532 nm. Attempts were made to use these ITO-coated plastic substrates for the fabrication of a organic light-emitting device that was based on single-layer, molecularly doped (poly(N-vinyl carbazole)) (PVK) with a mixture of tris(8-hydroxyquinoline) aluminum (III) (Alq₃) and N,N'-bis (3-methylphenyl)-N,N'-bis-(phenyl)-benzidine (TPD) of 1:1 ratio.     

Research and Progress in Laser Welding of Wrought Aluminum Alloys. I. Laser Welding Processes

With the wide application of Al alloys in automotive, aerospace and other industries, laser welding has become a critical joining technique for aluminum alloys. In this review, the research and progress in laser welding of wrought Al alloys have been critically discussed from different perspectives. The primary objective of this review is to understand the influence of welding processes on joint quality and to build up the science base of laser welding for the reliable production of Al alloy joints. Two main types of industrial lasers, carbon dioxide (CO₂) and neodymium-doped yttrium aluminum garnet (Nd:YAG), are currently applied but special attention is paid to Nd:YAG laser welding of 5000 and 6000 series alloys in the keyhole (deep penetration) mode. In this part of the review, the main laser welding processing parameters including the laser-, process-, and material-related variables and their effects on weld quality are examined. In part II of this article in this journal, the metallurgical microstructures and main defects encountered in laser welding of Al alloys such as porosity, cracking, oxide inclusions, and loss of alloying elements are discussed from the point of view of mechanism of their formation, main influencing factors, and remedy measures. In part II, the main mechanical properties such as hardness, tensile, and fatigue strength and formability are also discussed.     

Research and Progress in Laser Welding of Wrought Aluminum Alloys. II. Metallurgical Microstructures, Defects, and Mechanical Properties

With the wide application of aluminum alloys in automotive, aerospace, and other industries, laser welding has become a critical joining technique for aluminum alloys. In this review, the research and progress in laser welding of wrought aluminum alloys are critically discussed from different perspectives. The primary objective of the review is to understand the influence of welding processes on joint quality and to build up the science base of laser welding for the reliable production of aluminum alloy joints. Two main types of industrial lasers, carbon dioxide (CO₂), and neodymium-doped yttrium aluminum garnet (Nd:YAG), are currently applied but special attention is paid to Nd:YAG laser welding of 5000 and 6000 series alloys in the keyhole (deep penetration) mode. In the preceding article of this review (part I), the laser welding processing parameters, including the laser-, process-, and material-related variables and their effects on welding quality, have been examined. In this part of the review, the metallurgical microstructures and main defects encountered in laser welding of aluminum alloys such as porosity, cracking, oxide inclusions, and loss of alloying elements are discussed from the point of view of mechanism of their formation, main influencing factors, and remedy measures. The main mechanical properties such as hardness, tensile and fatigue strength, and formability are also evaluated.     

532 nm Nd:YVO4/KTP激光器的I2分子吸收谱线的观测及频率稳定的研究

激光二极管抽运的固体激光器可用于光学计量,长度测量,相干光通信,激光雷达等方面,高精度应用要求激光器的频率稳定。碘分子在５３２ｎｍ附近在上百条强的吸收谱线,采用单频Ｎｄ;ＹＶＯ４／ＫＴＰ激光对碘的一些吸收谱线作了观测,并进行了激光频率稳定的研究,这些吸收谱线是１９９７年９月国际米定义咨询委员会推荐作为频标的９组５３２ｎｍ碘吸收谱线之外的新的参考谱线。     

脉冲激光离散加工熔池形态及其影响因素的研究

研究了Ｎｄ：ＹＡＧ脉冲激光离散加工时功率密度和作用时间对熔池几何形态的影响，５ＣｒＭｎＭｏ钢的实验结果表明：在本文所涉及的加工条件下，熔池存在的热传导型和深熔型两种形态；激光作用时间小于４ｍｓ时，在相同作用时间下，随着激光功率密度的增加，熔池深宽比显著增加；但当作用时间大于４ｍｓ后，功率密度对深宽比的影响减弱，基于线性热传导模型的计算结果表明：熔凝起始阶段的固态加热过程可忽略；熔和何尺寸在激光脉冲