La2Ce2O7@La2Zr2O7核壳结构纳米粉体的 制备及其抗烧结性能

针对La_2Ce_2O_7抗烧结性能较差,La_2Zr_2O_7的热膨胀系数较低的性能特点,采用水热法合成了La_2Ce_2O_7内核,然后通过共沉淀法成功制备La_2Ce_2O_7@La_2Zr_2O_7核壳结构纳米粉体.将粉体预压成块,分别在1 100℃、1 300℃和1 500℃下进行了不同时间的烧结测试及在1 100～1 500℃烧结6 h以考察温度对其抗烧结性能的影响.采用扫描电镜、透射电镜、能谱仪分析了材料的形貌和成分,并测试了试样的密度和显微硬度.结果表明,La_2Ce_2O_7内核具有立方结构或八面体结构外形,粒径约200 nm. La_2Zr_2O_7壳层为非晶体,形成了包覆效果良好的La_2Ce_2O_7@La_2Zr_2O_7核壳结构.等温烧结时,核壳结构的密度变化率保持在2.1%以内,远低于La_2Ce_2O_7和La_2Zr_2O_7,孔隙和晶粒尺寸分布均匀,无裂纹和烧结现象出现.当烧结温度在1 300℃以内时,核壳结构组织均匀,多孔,密度变化率稳定在10.6%以内,晶粒尺寸约维持在450nm,晶粒长大速率与La_2Zr_2O_7接近,抗烧结性能良好;当烧结温度高于1 300℃时,核壳结构孔隙增大且晶粒迅速长大,致密化加快,晶粒长大速率也变快,与La_2Ce_2O_7接近,出现明显烧结现象;其显微硬度稍高于La_2Ce_2O_7,而远低于La_2Zr_2O_7.     

原子团簇对飞秒激光的吸收

使用800nm飞秒脉冲激光研究了Xe,Ar,He等原子团簇对激光的吸收.实验结果表明,脉冲阀门的工作压力、所使用的气体种类等因素对团簇的尺寸及团簇对激光的吸收影响很大.在阀门工作压力为20×10⁵Pa、激光功率密度为1×10¹⁵W/cm²的条件下,Xe团簇对激光的吸收高达45%.激光预脉冲的存在会降低原子团簇对激光能量的吸收.离子能量测量结果表明,团簇对激光的高效吸收导致较高离子温度等离子体的生 关键词： 原子团簇 飞秒激光 能量吸收效率 高能离子     

TEMPORAL CHARACTERIZATION OF LASER PULSES FROM JIGUANG-I LASER FACILITY WITH A COMPACT DUAL FUNCTION AUTOCORRELATOR

An optical pulse autocorrelator for rapid and slow scanning is described in this paper. Using an audio loudspeaker on one arm, an interferometric rapid-scanning signal of the output from a high-repetition laser oscillator is obtained. However, by adjusting the positions of the mirrors and using a step-motor on another arm, the intensity autocorrelation function of the output from a low-repetition laser amplifier can be easily measured. Using all-reflecting optics and an adequate nonlinear crystal, the whole instrument is very compact and has been used to measure sub-20 fs light pulses in both configurations with excellent agreement. In the slow-scanning configuration, a pulse train as long as 500ps has been determined. Using this autocorrelator, the home-made JIGUANG-I CPA laser facility was characterized for its pulse duration evolution.     

飞秒激光在BBO晶体中倍频效率的数值计算

采用分步傅里叶法对飞秒激光在BBO晶体中倍频过程的效率进行了数值计算,分析表明这种方法既避免了其他数学方法的繁琐,又直观地展现了倍频过程的物理本质.针对有关实验条件,计算了脉宽为100fs的激光脉冲通过2mm长、Ⅰ类相位匹配的BBO晶体的倍频效率,计算结果与实验上对同样晶体倍频效率的测量是一致的. 关键词： 飞秒激光 倍频     

4.5MW小型化全固态腔倒空飞秒掺钛蓝宝石激光器

研制了国内首台腔倒空克尔透镜自锁模掺钛蓝宝石激光器,该激光采用二极管抽运的全固态连续波532nm激光抽运.在5.4W的抽运功率下,获得了峰值功率大于4.5MW、脉宽小于18fs的稳定锁模脉冲,其重复频率可低至20kHz,所占尺寸约53.5cm×20.5cm.据知,此结果是迄今重复率最低、结构最紧凑的声光腔倒空飞秒激光器件 关键词： 掺钛蓝宝石 腔倒空 飞秒脉冲 克尔透镜锁模