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题名	时空聚焦飞秒激光脉冲的特性与应用研究
作者	王朝晖
学位类别	博士
答辩日期	2016
授予单位	中国科学院上海光学精密机械研究所
导师	程亚
关键词	飞秒激光脉冲 时空聚焦 干涉测量 等离子体 纳米光栅
其他题名	Investigations on Characteristics and Applications of Spatiotemporally Focused Femtosecond Laser Pulses
中文摘要	近年来，飞秒激光微加工技术以其对透明材料的三维加工能力被广泛地应用于微光学、微流体、微电子学等领域。同时人们发现飞秒激光与透明材料相互作用过程中会产生许多有趣的现象， 包括折射率的修饰、纳米孔洞、纳米光栅结构的形成以及非互逆直写效应等。 为了从时间域和空间域精确地操控飞秒激光与透明材料的相互作用，人们发明了多种飞秒脉冲整形技术，包括空间整形技术、时域整形技术、偏振整形技术以及时空聚焦技术等。 其中飞秒激光时空聚焦技术在微纳加工中的应用引起了广泛的关注， 利用该技术可以获得各向同性的直写加工分辨率，抑制焦点以外的非线性效应。 最近的研究发现时空聚焦的飞秒脉冲具有独特的光场特征，包括脉冲前沿倾斜和光强平面倾斜。 与此同时，人们发现时空聚焦脉冲与介质相互作用时会产生许多新奇的现象， 例如在透明材料中的非互逆直写效应， 以及在中心对称的气体介质中产生二次谐波等。 虽然最近的研究已经证明这些现象与焦点处的脉冲前沿倾斜有关，但时空聚焦飞秒脉冲与材料相互作用的完整物理图像目前尚不清晰，其独特的光场特性尚未得到有效的利用。 基于上述研究背景，本论文对飞秒激光时空聚焦的光场特征进行深入研究，在此基础上对时空聚焦的飞秒激光与透明材料相互作用进行实验探索。主要工作和创新性成果如下： 1. 提出了一种飞秒激光时空聚焦脉冲焦点处脉冲前沿倾斜的干涉测量技术。该技术引入传统聚焦的参考脉冲与时空聚焦脉冲在焦点处发生干涉。通过测量焦平面干涉条纹的空间位移与两个脉冲的相对延时之间的关系，实现对时空聚焦脉冲的脉冲前沿倾斜的精确测量。实验证明该技术对于焦点位于空气中或透明材料内部的情况均适用，因此该技术可以对脉冲与透明材料相互作用的区域直接进行测量，对进一步研究时空聚焦脉冲与透明材料的相互作用有重要意义。 2. 利用飞秒激光泵浦-探测阴影成像技术，对时空聚焦飞秒脉冲在熔融石英内部诱导等离子体的产生与演化过程进行时间分辨成像。发现等离子体轨迹相对于脉冲传播的方向有一定角度的偏折，引起这种现象的原因是焦点处脉冲前沿倾斜造成的等离子体不对称分布。 由于电离是时空聚焦飞秒脉冲诱导透明材料改性的最基础过程，该研究有助于从本质上揭示非互逆直写等现象的物理图像，并对时空聚焦技术在微纳加工中的应用有指导意义。 3. 分别利用时空聚焦和传统聚焦的飞秒激光在多孔玻璃内部诱导纳米光栅，发现时空聚焦的情况下纳米光栅具有不对称的空间分布。通过对纳米光栅的演化过程进行系统研究，发现其独特的不对称空间分布源自于时空聚焦光场固有的强度平面倾斜。该研究对进一步理解纳米光栅形成的物理机制有重要意义，并为纳米光栅形态的操控提供了有效手段
英文摘要	Recently, femtosecond laser micromachining has been widely applied in many research fields such as microoptics, microfluidics and microelectronics for its unique capability of three-mensional microfabrication inside transparent materials. In the meanwhile, it was discovered that interaction of femtosecond laser pulses with transparent materials can lead to many interesting phenomena, such as refractive index modification, formation of nanovoids and nanogratings, and nonreciprocal writing. For precisely manipulating the interaction of femtosecond laser with transparent materials in both spatial and temporal domains, several femtosecond pulse shaping techniques have been developed, including spatial pulse shaping, temporal pulse shaping, pulse polarization control, and spatiotemporal focusing. In particular, applications of spatiotemporal focusing technique in femtosecond laser micromachining has attracted much attention, for such technique allows three dimensional isotropic fabrication resolution, eliminates nonlinear effect out of focus. It has been discovered by several recent investigations that the spatiotemporally focused pulse has some intriguing characteristics, including a tilted pulse front and a tilted peak intensity plane. In the meanwhile, it was found that the interaction of spatiotemporally focused pulse with solid or gaseous media can lead to several interesting phenomena, such as the nonreciprocal writing in transparent materials and second harmonic generation in centrosymmetric gas media. Although it has been confirmed by several recent researches that these phenomena have direct connection with pulse front tilt of spatiotemporally focused spot, the complete physical picture behind them is still lacking, and the unique characteristics of spatiotemporally focused pulse has not been completely utilized. Based on these considerations, in this thesis we make an intensive study on the characteristics of spatiotemporally focused pulses, and on this basis we make experimental exploration on the interaction of spatiotemporally focused femtosecond pulse with transparent materials. The main results and innovations of this thesis are listed as follows: 1. An interferometric measurement technique of pulse front tilt of spatiotemporally focused femtosecond laser pulses is developed. A conventional focused pulse is introduced as a reference pulse, and interference occurs in the focal plane between the reference pulse and spatiotemporally focused pulse. Accurate measurement of pulse front tilt is achieved by examination of the spatial displacement of the interferometric fringe as a function of time delay between the two pulses. It is confirmed by the experiment that such technique is applicable when the pulse is focused in air or transparent materials. Thus the measurement can be directly made in the interaction site of the pulse with transparent materials, which has important significance to make further investigations on the interaction of spatiotemporally focused pulses with transparent materials. 2. Time-resolved shadowgraphs of the generation and evolution of plasma induced by spatiotemporally focused femtosecond laser pulse in fused silica glass are made using a pump- probe shadow imaging technique. The observation shows that the track of the plasma is curved with respect to the direction of the pulse propagation, which is attributed to an asymmetric density distribution of the transient plasma produced in the focal volume caused by the pulse front tilt. As the photoionization is the most fundamental process in the modifications in transparent materials with spatiotemporally focused pulses, such investigation is beneficial to reveal the substantial physical picture of the nonreciprocal writing, and instructive to the applications of spatiotemporal focusing technique in femtosecond laser micromachining. 3. In-volume nanogratings are formed in porous with both conventionally and spatiotemporally focused femtosecond laser pulses, and it is discovered that in the case of using the spatiotemporally focused laser, the nanoplanes in the nanogratings are asymmetrically distributed. Based on the systematic investigations on the formation of the nanogratings, it is revealed that the asymmetrical distribution originates from the intensity plane tilt in the spatiotemporally focused spot. Such investigations have important significance to further understanding of the physical mechanism behind the nanograting formation, and provide an effective approach on the controlling of geometries of nanogratings.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15999]
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	王朝晖. 时空聚焦飞秒激光脉冲的特性与应用研究[D]. 中国科学院上海光学精密机械研究所. 2016.

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