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题名	飞秒激光的达曼光栅分束研究
作者	李国玮
学位类别	硕士
答辩日期	2005
授予单位	中国科学院上海光学精密机械研究所
导师	周常河
关键词	飞秒激光脉冲 达曼光栅 二元光学
其他题名	Research of splitting femtosecond laser pulses by using a Dammann grating and compensation gratings
中文摘要	飞秒激光脉冲具有高的功率、超短脉冲持续时间的特性，使之在物理、化学、生物等领域都有着重要的应用。 对飞秒光束进行分束时，通常的分束装置有半透半反镜或角锥反射镜。这两种分束器只能实现一束光分成两束光。半透半反镜会将材料色散的作用引入分束后透射输出的光束；角锥反射镜是通过将两反射面相交的棱放置在光束的中心，在空间上实现光束左右两边分离，这样原本的光束中心就变成了分束后光束的边缘。 本论文的创新工作包括达曼光栅分束、测量飞秒激光脉冲两项内容。首先是设计了一种利用达曼光栅高效率、大规模分束飞秒激光脉冲的方案；其次是实验搭建了反射式lx2偶数达曼光栅分束装置，利用飞秒激光频率分辨多发光学扫描（Multi一shot FROG）方法，得到了原始脉冲的时频域信息。 使用达曼光栅直接分束飞秒激光脉冲时，由于飞秒光脉冲是多频谱的，分束得到的各个衍射级次光束中不同频率的光波具有不同的衍射角，无法实现需要的分束效果。我们设计了一种新颖的方法，即达曼光栅第m，衍射级次的光束被光栅密度是达曼光栅密度ml倍的补偿光栅补偿，可以得到无角色散的阵列输出的飞秒光束，从而实现一束飞秒光分成多束飞秒激光，即高效率地分束。在飞秒激光带宽不是极大时，用达曼光栅分束装置分束得到的输出脉冲宽度变化极小。该分束装置对光束的空间频谱走离作用虽然总是存在，但是其影响很小；而且如果分束得到的光束被透镜聚焦，在焦面上空间频谱走离作用会完全消失。如果采用反射式光栅实现达曼光栅分束装背，还可以彻底避免飞秒光通过介质材料时所带来的材料色散影响。另外，用达曼分束器分束得到的相应正、负衍射级次的光束光脉冲是完全一样的。这种全新的飞秒激光分束装置将在飞秒激光多点加工、飞秒脉冲测量、泵浦探测技术中具有潜在的应用价值。该工作已申请国家发明专利，论文发表于JOSAA，2005 22（4），767-772。 实验搭建了利用反射式1X2偶数达曼光栅分束对飞秒脉冲频率分辨光学扫招；多发测量装粉，实验得到了FROGC时谱图，并用FROG重构程序反演出了飞秒脉冲的时频域信息。反射式达健光栅分束器具有很强的耐破坏域值：采用反射式达坐光栅分束器分束坛秒激光，可以避免材料色散的影响：采用不同的光栅深度，可以使该分束装置适用于不同的波段。结果表明，达曼分束装置不仅可以用于多发频率分辨光学扫描装置，还可以用在其它飞秒脉冲测量装置当中。该工作已申请国家发明专利。
英文摘要	A femtosecond laser pulse is characterized by high power and ultrashort pulse durations, characteristics that have important applications in fields such as physics, chemistry, biology, etc. The general beam splitters, used to split a beam of femtosecond laser pulses, are a conventional beam-splitter or a reflective one, an edge with two reflecting surfaces. Those kinds of beam splitters just can split an input beam in two beams of output. A beam-splitter substrate will introduce material dispersion in the transmitted one. The reflective one is placed in the middle of the input beam and spatially splits the beam in two, making the center of the input become the edge of the output. The novel works in this thesis include splitting and measuring femtosecond laser pulses by using Dammann gratings. Firstly, we proposed a novel scheme for highly-efficient splitting of femtosecond laser pulses; then we proposed a 1X2 array Dammann beam splitter for implementation of Multi-shot Frequency Resolved Optical Gating (FROG) and obtained the full characterization of the pulses both in time and frequency domains. When a Dammann grating is used to split a beam of femtosecond laser pulses, angular dispersion will occur in beams of each order of diffraction because the incident ultrashort pulse contains a broad range of spectral bandwidths. We propose a novel method in which the angular dispersion can be compensated by positioning an w-time-density grating to collimate the wth-order beam that has been split, producing an array of beams that are free of angular dispersion. The increased widths of the compensated output pulses are not obvious. Although the lateral walk-off always exists, its effect is very small if the spectrum bandwidth is not extremely large; and it will be removed at the focus plane when we focus the split beam. This method can be free of material dispersion when reflective Dammann and compensation gratings are adopted and the positive- and negative- diffraction-order beams are equal to each other. This method should benefit processing the workpiece concurrently at multiple points, femtosecond pulse measurement, pump-probe femtosecond spectroscopic techniques, etc. This work has applied a Chinese invention patent and the paper has been published in JOSA A 2005, 22(4), 767-772. We used a 1 X 2 reflective Dammann splitter in multi-shot FROG and obtained experimental-FROG spectrograms. Using the FROG algorithms and the experimental spectrogram, we retrieved the full characterization of the femtosecond laser pulse in both time and frequency domains. The reflective Dammann splitter has strong damage threshold value, the material dispersion can be avoidable, and the splitter is fit for different frequency range if the grating is etched in corresponding depth. The experiment shows that the Dammann splitter can be used not only in the multi-shot FROG, but also in the other pulse-measurement methods. This work has applied a Chinese invention patent.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16642]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	李国玮. 飞秒激光的达曼光栅分束研究[D]. 中国科学院上海光学精密机械研究所. 2005.

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