金属微细槽在电子、通信、航空航天、生物医学等领域有着广泛的应用。超快激光加工在100μm及以下尺寸的微细槽加工中具有较大的潜力。为了提高金属微细槽的加工精度和加工质量,减小槽壁斜度,采用空间整形飞秒激光加工的方法,应用空间光调制器将高斯光整形为矩形平顶光,在高温合金上进行微细槽加工实验。结果表明,空间整形飞秒激光加工微细槽的槽壁斜度相较于高斯光束的加工结果明显减小,加工质量明显提高。此外,采用该方法分别加工了宽度为10,20,150μm的深槽,结果显示,深槽槽壁截面未出现明显的热影响区域,说明该方法具有卓越的加工能力和极大的应用潜力。

激光凭借其穿透性和高强度的独特优势，已在加工领域得到广泛应用，但为了实现激光加工的高效率、高精度指标，需要对激光进行空域整形和时域整形。空域整形技术主要是基于折射原理、衍射原理或偏振原理的整形技术，时域整形技术主要包括脉冲压缩技术和脉冲序列控制技术。

通过将1 kHz重复频率的飞秒放大激光脉冲耦合到大芯径(100 μm)阶跃光纤, 在27 mm长的光纤中产生了环形空间光强分布, 并在3 160 mm的长光纤中观察到平台型的空间光强分布, 通过自聚焦效应对该现象进行了解释.结果表明,通过选择合适的光纤, 可以实现对放大飞秒激光脉冲的有效空间整形, 从而达到改善光束质量的效果.

为了获得更高功率的输出激光脉冲, 需要将注入到主放大链的种子脉冲进行光谱整形来补偿放大过程中的增益窄化效应。利用展宽器中啁啾脉冲的光谱具有空间排布的特点, 采用石英晶体平凸透镜空间光强度调制器间接地实现窄带激光脉冲的光谱整形, 在展宽器的输出端获得了光谱呈平顶分布的种子啁啾脉冲。通过调节偏振片的透偏方向, 可方便地调谐输出脉冲光谱的形状。

In order to improve the energy efficiency of the inertial confined fusion (ICF) high-power laser system and use the optical energy sufficiently, it is necessary to convert Gaussian laser beam into uniform beam, or into parabolic-like beam to precompensate the spatially dependent gain of the Nd∶glass amplifiers, for the sake of uniform output distribution at the target. The intensity control is obtained with panels composed of binary pixelated arrays of metal pixels, which was designed by error diffusion method. The shaping effect is numerically simulated. The factors, which will influence the shaping effect, such as mismachining of the panel and size of the pinhole of the spatial filter are discussed. An anti-gaussian distribution and a parabolic distribution binary panels are fabricated. The experimental shaping result is given and the error is analyzed. Binary panels are proved to be excellent shaping elements in modeling the intensity of laser.

为了提高高功率激光系统的整体效率和充分利用光能,需要对前端注入的高斯光束进行空间整形,实现驱动器终端激光的均匀化输出。采用振幅型二元面板对激光光束进行空间强度整形,利用误差扩散法进行了理论设计,数值摸拟了整形效果,同时讨论了面板加工误差以及空间滤波器的小孔大小等因素带来的影响。根据理论设计,分别加工了反高斯透射率分布和抛物线透射率分布的二元面板,并进行了整形实验,实现了各自的整形功能,并做了误差分析。实验证明二元面板能对激光光束的空间强度分布实现了精确的整形。

在保持间接驱动光束排布结构及束数不变的条件下,通过对各路入射光横截面强度分布进行调整,消除多光束叠加后球靶表面光强大尺度的不均匀性。建立了描述球靶表面多光束叠加分布的计算机模拟平台。根据光束入射条件,计算出多束光在靶面叠加后的光强分布及其不均匀度。利用加权平均的思想,得出实现均匀强度叠加所需要的各入射光焦面强度分布状态。根据激光传输理论,计算出可实现球靶均匀辐照的进入靶室聚焦透镜之前的光电场分布。

In order to take full advantage of amplifier gain-bandwidth, and obtain a shorter pulse with higher power in the terminal, it is necessary to conduct a spectrum shaping before the seed pulse being injected into the main amplifier chain to compensate the effect of gain narrowing. A new method, based on the spatial grating with variable line-space for spectrum shaping of chirped laser pulse with the central wavelength at 1053 nm and line width 6 nm, is presented. The rigorous coupled-wave theory is used to analyze the characteristics of grating diffraction, and the results indicate that this method produces no phase distortion. The diffraction efficiency, as a function of the depth and period of groove, incidenct angle, and incident wavelength, is calculated and analyzed, respectively. With proper grating parameters, the spectrum modulation depth from 0.5% to 84% can be achieved.

为了充分利用放大介质的增益带宽, 获得脉宽更短, 功率更高的输出脉冲, 需要将输入到主放大链的种子脉冲进行光谱整形来补偿放大过程中的增益窄化效应。提出了利用变栅距反射光栅实现中心波长1053 nm, 谱宽6 nm啁啾脉冲的光谱整形。运用严格的光栅衍射耦合波理论分析光栅的衍射特性, 发现该方案不会引入相位畸变。分别计算和分析了刻槽深度、入射角大小、光栅周期以及入射光波长的变化对衍射效率的影响, 通过选取适当的光栅参量可获得0.5%～84%的光谱调制深度。