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题名	周期量级超短脉冲宽度和载波包络相位测量技术研究
作者	许灿华
学位类别	博士
答辩日期	2012
授予单位	中国科学院上海光学精密机械研究所
导师	李儒新 ; 冷雨欣
关键词	周期量级脉冲 FROG技术 载波包络相位测量 金属光电离
其他题名	Study on the duration and carrier-envelope phase measurement for few cycle ultrashort laser pulses
中文摘要	随着超短脉冲激光技术的发展，近红外波段的激光脉冲宽度已经达到光学周期量级。借助于光学参量放大（OPA）等技术，载波包络相位（CEP）稳定的周期量级超短脉冲的光谱可以扩展到中红外新波段，并在产生高次谐波等过程中有大量应用。对该波段超短脉冲宽度和CEP的测量不仅有助于周期量级脉冲的产生，而且对研究光与物质的相互作用有重要意义。此外周期量级超短脉冲的光电场不仅与能量、脉冲宽度以及聚焦条件有关，还与CEP密切相关。采用光学干涉和电子学反馈等技术可以很好地控制近红外周期量级脉冲的CEP稳定性，但CEP绝对值的测量则需要借助于光与物质的相互作用中的CEP效应来完成。周期量级脉冲的测试技术直接反映了人们对超短脉冲激光的操控和使用的能力，一直是强场激光领域最前沿的课题之一。 本论文主要工作包括三部分：一是针对实验室中现有的1kHz，1.8 m波段的OPA系统，搭建了一套该波段周期量级脉冲宽度和相位测量的频率分辨光学快门装置（FROG），对脉冲宽度进行测量和优化；二是利用CEP可控的钛宝石振荡器产生的0.8 m波段的周期量级激光脉冲对金膜样品进行光电离实验，分析光电流的特征，并探索CEP效应；三是用同样的CEP可控的0.8 m波段的周期量级激光脉冲对金属纳米钨针进行光电离实验，分析其光电流特征和CEP效应。其中第一项工作在本所完成，后两项的实验工作主要在德国马普学会的Fritz-Haber研究所完成。本论文的主要工作和创新点包括： 1、在实验上成功搭建1.8 m波段周期量级脉冲宽度和相位单发测量的FROG装置，其创新点在于：采用空间分光的方法代替传统的分光片将待测脉冲分成两个子光束，可以使待测脉冲在非线性晶体之前不经过任何透射元件，避免引入附加色散；采用非共线结构结合4f成像系统将两个子脉冲时间上的延时投影到CCD的空间坐标上，实现单发测量的功能，这对于低重频的激光放大系统的监测尤为重要。本论文还采用Matlab编写主矩阵元广义投影算法对测量的FROG图谱进行反演计算，得到可靠的脉冲宽度和相位信息。 2、首次在空气中进行金属样品的光电离实验，探索在实验室环境下实现低能量振荡器脉冲CEP绝对值测量的方法，主要的内容包括：系统地分析现有的CEP绝对值测量方法；在外加直流偏压下采用CEP可控的Ti:sapphire振荡器脉冲对特殊制备的粗糙的金膜样品进行光电离，得到比光滑金膜样品大两个量级以上的光电流；通过大量的实验分析了光电流和外加偏压以及激光功率的依赖关系，研究光电离主要机制和非线性阶数；采用光学自相关的方法研究金膜样品对周期量级激光的时间和光谱的响应；最后通过外加的电信号调制激光脉冲的CEP周期性的变化，观察光电流随着CEP的变化情况，讨论在空气中用金膜样品光电离作为CEP探测手段的可能性。 3、首次开展空气中的纳米钨针光电离研究，分析其电离的机制以及激光脉冲CEP变化对光电流的影响，主要内容包括：理论上分析了外加直流电场在纳米钨针上的几何增强及其对光电离效率的影响；通过化学腐蚀方法制备纳米量级的钨针，并在负偏压下进行光电离实验，研究光电流随着激光功率和偏振的变化，分析光电离的主要机制；通过光学自相关方法发现光电离的非线性阶数与激光焦斑在钨针上的位置密切相关；通过外加电压调制激光脉冲的CEP，观察光电流的CEP效应，讨论在空气中由于场强增强效应导致的光电流中存在大量随机放电现象对CEP测量的影响。
英文摘要	With the development of ultrashort laser pulse technology, the few-cycle duration laser pulse in near-infrared range has been achieved. Benefit from the optical parametric amplifier (OPA) technology, the spectrum of few-cycle ultrashort laser was expanded to mid-infrared region, and was applied extensively in the high harmonic generation. Precise measurement of the duration and phase of mid-infrared few-cycle pulse is important for its generation and its applications in light-matter interactions. The electric field of ultrashort laser is related to the energy, pulse duration, focusing condition and special carrier-envelope phase (CEP) in few-cycle regime. Recently the CEP stability can be controlled by optical interference combined with electrical feedback, while the detection of the absolute CEP value depends on the CEP effect during the light-matter interaction. The characterization of few-cycle pulse marks people’s ability to manipulate the ultrashort laser. The relevant technologies are continuously attracting extensive attentions in strong field physics. The work of the thesis includes three parts: firstly, we built a single shot FROG apparatus to measure and optimize the duration of the home-made 1kHz, 1.8μm few-cycle OPA pulse. Secondly the photoionization of gold film was studied in air based on 0.8μm few-cycle Ti:sapphire oscillator. Finally the photoionization of the tungsten nanotip was carried out with same laser in air.The first part were finished in SIOM, the following two experiments were accomplished in Fritz-Haber Institute of Max-Planck Gesellschaft. Main results andinnovative points are listed as following: 1. We successfully built a single-shot FROG apparatus for the measurement of duration and phaseof 1.8μm few-cycle laser, The innovative technologies include:in the FROG apparatus, spatially light splitting was used to avoid inducing additional dispersion to the measured pulse before nonlinear crystal; Combining nonlinear sum-frequency configuration with 4f imaging, the delay of two sub-beam was projected to the space axis of CCD camera, therefore fulfilled the demands of single-shot measurement. In the thesis, the algorithm based on PCGPA was programmed in Matlab, and used to obtain the reliable pulse duration and phase information. 2. For the first time, we implemented the experiments of metal’s photoionization in the air, and explored the detection means of CEP absolute value for low energy laser oscillator in the ambient condition. The main work includes: the methods of absolute CEP measurement were introduced systematically; few cycle Ti:sapphire laser photoionization of gold film with bias DC voltage was studied;the bias dependence and the laser power dependence of the photocurrent were analyzed to figure out the photoionization mechanism and nonlinear order; autocorrelation method was used to research the temporal and spectral response of the sample; and finally the CEP effect of the photocurrent was discussed based on laser’s CEP modulation generating by an external periodical electric signal. 3. For the first time, we implemented the photoemission of nanosize tungsten tip in the air,analyzed the photoionization mechanism and the CEP effect of the photocurrent. This part incudes:theoretically simulate the field enhancement of DC bias on nanosize tungsten tip; applying a negative bias, laser power and polarization dependence of the photocurrent were utilized to classify to mechanism;the nonlinear order of the photoionization was found to be very sensitive to the position of the laser focus; finally the influence of tip’s random discharging to the CEP measurement was discussed.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15689]
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	许灿华. 周期量级超短脉冲宽度和载波包络相位测量技术研究[D]. 中国科学院上海光学精密机械研究所. 2012.

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