偏振对飞秒激光辐照LiF晶体的影响

飞秒激光聚焦到LiF晶体内部, 晶体的加工形貌随偏振改变. 实验表明, 偏振方向平行于<110> 晶向时, 加工起点到表面的距离是<100>偏振下的1.08 倍; 而<110>偏振下加工终点到表面的距离是<100> 偏振下的1.01 倍. 为了解释加工形貌的偏振依赖, 建立了逆韧致辐射、雪崩电离和无辐射跃迁的模型, 首先, 价带电子通过强场电离和雪崩电离, 从激光中吸收能量跃迁到导带, 该过程用电子密度演化方程和傍轴非线性薛定谔方程描述, 求解方程得到导带电子密度; 其次, 导带电子通过无辐射跃迁过程释放能量给晶格, 由能量守恒计算出晶格温度沿激光传播方向的分布; 最后, 晶格温度超过熔点以上的区域被加工. 模拟结果显示, <110>偏振下加工起点到表面的距离是<100> 偏振下的1.03倍, 而<110>偏振下加工终点到表面的距离是<100>偏振下的0.981 倍, 与实验结果基本一致. 虽然Z扫描技术测量的非线性折射率随偏振方向变化, 但是非线性折射率的变化趋势与实验结果相反. 模拟和实验证明逆韧致辐射导致加工形貌随偏振变化.     

新型脉冲CO2激光器预电离测量参量研究

对5 kW横流CO₂激光器脉冲预电离过程进行理论分析和实验研究.表明了预电离过程中电子密度的重要作用,它能为下一步的主放电提供良好的条件.结果表明理论分析与实验结果相符合.     

Fabrication of Microstructures in LiF Crystals by a Femtosecond Laser

We report the space-selective formation of colour centres and refractive index change in LiF crystals at room temperature by an 800nm Ti:sapphire femtosecond laser irradiation. Optical absorption and photoluminescence spectra have been measured for the crystal before and after the laser irradiation. The absorption spectra indicate F and F3^ colour centres are induced in LiF after the laser irradiation. When the temperature of heat treatment reaches 300℃, the absorption peak disappears, indicating that the induced colour centres are bleached. The induced refractive index change is also evaluated. A mechanism for the formation of colour centres and refractive index change is proposed.     

Facile preparation of silver nanoparticles in bulk silicate glass by high-repetition-rate picosecond laser pulses

One-step precipitation of Ag nanoparticles in Ag+-doped silicate glasses was achieved through a focused picosecond laser with a high repetition rate. Absorption spectra and transmission electron microscopy(TEM) confirmed that metallic Ag nanoparticles were precipitated within glass samples in the laser-written domain. The surface plasmon absorbance fits well with the experimental absorption spectrum. The nonlinear absorption coefficient β is determined to be 2.47 × 10-14 m/W by fitting the open aperture Z-scan curve, which originated from the intraband transition in the s-p Ag band. The formation mechanism of Ag-glass nanocomposites is discussed as well.     

Self-organized voids revisited:Experimental verification of the formation mechanism

We conduct several experiments to further clarify the formation mechanism of a self-organized void array induced by a single laser beam, including energy-related experiments, refractive-index-contrast-related experiments, depth-related ex- periments, and effective-numerical-aperture experiment. These experiments indicate that the interface spherical aberration is indeed responsible for the formation of void arrays.     

激光束在大气中长距离传输聚焦特性的研究

研究了大气湍流与热晕对于几种不同波长激光束的的长距离传输聚焦特性的影响。光束质量与光束漂值的理论与实验值基本一致。     

自适应控制飞行光学聚焦特性

 在对高阶模飞行光学聚焦特性进行研究的基础上，提出了应用自适应飞行光学聚焦系统来解决飞行光学聚焦特性的问题，对自适应飞行光学聚焦系统的调节特性进行了数值模拟，结果表明该系统能够实现对长距离飞行光学激光加工过程中焦点位置与焦斑大小的控制。     

飞秒激光相干场诱导材料功能微结构

飞秒激光在整个脉冲宽度内具有极好的相干性，因而当从同一光束分出的两束或两束以上的光束时间与空间上实现相互叠加时将会形成强度周期性调制的电磁场．这种周期调制的电磁场与材料产生相互作用，能诱导出相应的周期微结构．最近通过两束或两束以上飞秒激光干涉诱导功能微结构得到了广泛研究．文章综合了国内外飞秒激光研究小组在干涉诱导微结构方面的一些最新成果以及作者在这方面开展的工作，对飞秒激光干涉技术的原理及其在诱导微结构方面的应用进行了介绍．     

飞秒激光诱导的Mn2+掺杂锗酸盐玻璃上转换发光

研究了室温下的飞秒激光诱导过渡金属Mn2+掺杂锗酸盐玻璃的上转换发光现象。样品的激发光谱与发射光谱表明,激发过程是能级6A(6S)→4E(4G)/4A1(4G)的跃迁,该过程源于Mn2+离子的4T1(4G)→6 A1(6 S)跃迁。由409 nm单色光激发样品得到的发射光谱与800 nm飞秒激光激发的光谱相一致。通过分析飞秒激光泵浦功率密度与荧光强度的依赖关系以及飞秒激光辐照样品前后的吸收谱,认为该上转换过程为双光子同时吸收过程。随着Mn2+浓度的提高,上转换发光的中心波长发生红移。     

利用多束飞秒激光干涉在金属箔和金属薄膜上形成阵列孔

报道了利用五束飞秒激光干涉，在镍箔和镀在玻璃上的铝膜上制备阵列孔的方法。光学显微镜和扫描电镜观察发现飞秒激光照射后在金属箔和薄膜上形成了微米量级的阵列孔。这一技术允许一步、大尺寸、微米量级的加工金属材料，具有潜在的工业应用价值。