飞秒激光诱导透明物质新现象的物理机制与应用
文献类型：学位论文
| 作者 | 钱滨 |
| 学位类别 | 硕士 |
| 答辩日期 | 2009 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 邱建荣 |
| 关键词 | 飞秒激光 单束 相互作用 非线性 微结构 透明介质 |
| 其他题名 | Mechanisms and applications of the novel femtosecond laser induced phenomena |
| 中文摘要 | 飞秒激光具有超短的脉冲宽度和极高的脉冲峰值功率，因此它可与透明介质产生高度非线性相互作用。虽然对于飞秒激光与透明介质相互作用的研究已经持续了十几年，但是仍有新的现象不断地被发现，并出现了很多具有创新性的成果。对单束飞秒激光诱导的各种新现象的深入研究为强场物理、等离子体物理、非线性光学和材料科学等基础学科的理论研究提供了新思路。 本文对1kHz和250kHz两种不同脉冲频率的飞秒激光与玻璃、晶体等透明介质的相互作用做了系统的研究，发现了一些全新的现象，对其形成机理作了探讨，对飞秒激光与透明介质的相互作用提出了一些新的看法。本文的主要创新性成果有以下几个方面： 1．首次在实验上发现，用紧聚焦的飞秒激光在CaF2内部沿着垂直于激光传输方向照射时，样品内部会形成斜十字形微结构；用飞秒激光在微结构附近再次辐照时，可以使先前的微结构部分消失。通过透射电镜观察，我们确认了微结构主要由高密度的局域位错组成，经激光二次辐照后，位错密度的大量减少导致部分微结构消失。我们对这种现象的机理作了进一步的探讨。这种利用飞秒激光在晶体内部制备和部分“擦除”位错的方法为我们发展位错技术提供了新思路。 2．我们成功地利用飞秒激光在闪烁晶体Bi4Ge3O12（BGO）中写入了波导。通过在BGO单晶中写入双线的方法，我们第一次实现了在闪烁晶体中的波导写入。波导的传输损耗为4.2 dB/cm。我们系统研究了激光功率和聚焦深度对微结构端面的影响。基于闪烁晶体特有的闪烁特性，我们探讨了未来其可能的应用，提出了全新的利用波导阵列代替BGO条状小块阵列应用于电子发射断层摄影(PET)系统的想法。由于波导的尺寸远远小于BGO小块，利用这种波导阵列取代BGO条状小块阵列可以大大提高成像系统的分辨率，因此具有极为重要的意义。 3． S. Kanehira等人用紧聚焦的单束飞秒激光在钠钙硅玻璃中持续辐照后，发现辐照区域及其周围区域的元素分布发生了明显的变化。他们发现玻璃的网络修饰体元素一般会在最外围形成一个元素富集圈，而网络形成体元素的分布则相反，对此他们提出了一种形成机理，认为飞秒激光诱发的冲击波在此过程中起到关键作用。但是我们通过实验发现在其他体系中，激光功率对元素分布具有决定性的影响。通过调节激光脉冲功率，我们实现了同种元素在玻璃中的各种分布，这个结果对于飞秒激光与透明介质的相互作用具有重大的意义。 |
| 英文摘要 | The interaction between femtosecond laser and transparent materials are usually based on nonlinear processes due to its ultrashort pulse and ultrahigh peak power. Although it has been more than ten years since femtosecond laser micromachining was first demonstrated in 1994, various new phenomena have been discoveried continuously. Further study of the femtosecond laser beam induced new phenomena is important for various fundamental sciences such as material science, plasma physics, high-field physics, nonlinear optics and etc. In this paper, two different repetition (1 kHz and 250 kHz) femtosecond lasers are applied to induce microstructures in transparent dielectrics including glass and crystal. We discovered some new phenomena, the corresponding mechanisms are also discussed. We focused on the following topics: 1. We reported for the first time that formation of microstructures (skewed cross-shaped patterns) which originated from local dislocations around the focal point in the bulk CaF2 single crystal induced by a single infrared femtosecond laser beam. Interestingly, it was observed that optically induced microstructures which originated from local dislocations could be partially erased by an additional irradiation of the femtosecond laser pulses on its neighboring area. Through the TEM bright-field image, we confirmed this phenomenon, in nanometer scale, by local dislocations vanishing. It can be used as a basic technique to open a field of dislocation technology. 2. We successfully fabricated a symmetric waveguide in Bismuth Germanate single crystal by writing double lines using femtosecond laser in it. Waveguide loss was measured to be as low as 4.2 dB/cm. Besides, we also investigated the influence of pulse energy and focal depth to the end face of irradiated regions. These buried BGO waveguide arrays maybe can be applied to replace the BGO segments in Positron emission tomography system in the future, which would improve the spatial resolution of PET system greatly. 3. S. Kanehira et al. reported that the distributions of ions in glasses are changed after infrared femtosecond laser irradiation. They discovered that the network modifying ions migrate from center region to outward. They reckon that the shock wave propagation plays a significant role in it. However, we discovered the abnormal micro-modification of ions distribution in glass induced by 250KHz infrared femtosecond laser beam. Results of electron probe microprobe analysis (EPMA) show that the distributions of ions changes obviously with different pulse energies. The mechanism for the femtosecond induced micro-modification of elements distribution has also been investigated. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16416]  |
| 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 | 钱滨. 飞秒激光诱导透明物质新现象的物理机制与应用[D]. 中国科学院上海光学精密机械研究所. 2009. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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