QQ客服 官方微博 反馈留言

题名	中红外周期量级激光脉冲驱动产生高次谐波中的载波-包络相位效应研究
作者	刁寒虎
学位类别	硕士
答辩日期	2014
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，曾志男
关键词	高次谐波 外激光 波-包络相位 绝对能量测量
其他题名	Research on carrier-envelope phase effects during high-order harmonic generation driving by mid-infrared few-cycle laser pulses
中文摘要	高次谐波的发现及发展是20世纪以来非常突出的科学成就，因为高次谐波不仅提供了一种产生相干深紫外光源和软X射线光源的非常有效的途径，而且还将我们研究微观动力学的时间尺度拓展到了前所未有的阿秒（1阿秒=10-18秒）尺度。近年来，中红外新波段周期量级激光的出现与迅猛发展，开拓了强激光场与物质相互作用的新物理与新效应的研究。当激光波长到达中红外波段时，决定原子光电离机制的Keldysh参数会显著降低，从而使得光电离深入到隧穿电离甚至深隧穿电离区域，进而产生一系列新物理现象和新效应。另一方面，与使用多周期激光脉冲不同的是，对于周期量级激光脉冲而言载波-包络相位(Carrier-Envelope Phase, CEP)变得至关重要，因此，中红外周期量级激光脉冲驱动产生高次谐波过程中的载波包络相位效应成为近年来强场物理领域的前沿热点之一。 本论文就是针对中红外周期量级光源，研究高次谐波产生过程中的CEP效应，包括谐波空间相干性的CEP效应，以及对比近红外与中红外周期量级激光脉冲驱动产生高次谐波的CEP效应的不同；另外，本论文还研究了高次谐波信号能量测量的方法。主要内容和创新点包括： 1、采用中红外周期量级光源作为驱动场，我们在实验上首次发现了谐波信号空间相干性的CEP效应。谐波信号的空间相干性随CEP周期性振荡，并且随着谐波级次的增大，相干性随CEP变化曲线的极值点会向CEP增大的方向移动。通过数值模拟发现，谐波产生时刻的等离子体密度导致的频率啁啾引起了该效应。 2、分别采用中红外周期量级激光脉冲以及近红外周期量级激光脉冲作为驱动场，我们对比了两种驱动场下稀有气体中高次谐波产生中的不同CEP效应。我们发现，对于中红外周期量级驱动光的情况，与CEP相关的高次谐波信号还与作用气体种类有关；并且在保持相同激光能量以及单脉冲周期数的情况下，两种驱动场下高次谐波产生的截止频率不同；同时数值模拟还显示，对于中红外场，主要是长电子轨道在作贡献，而近红外场主要是短电子轨道在作贡献。 3、搭建了一套用于测量高次谐波信号绝对能量的测量系统，弥补了目前市面上没有直接可用于高次谐波信号绝对能量测量的空白。
英文摘要	High Harmonic Generation (HHG) is a very outstanding breakthrough in the 20th century, for it not only provides a significant way to generate coherent XUV or X-ray light source, but also extends the time scale of microcosmic dynamics research to the never-before-accessed attosecond (1as=10-18s) level. Recently, with the appearance and rapid development of few-cycle mid-infrared laser pulses in the unconventional spectral band, it opens up the researches on the freshly physical phenomena about intense laser-matter interaction. When the wavelength of the driving field reaches mid-infrared band, the Keldysh parameter, which determines the types of the photon ionization, would drop to a much lower level. And it makes the photon ionization go to tunnel ionization region or even deep tunnel ionization region, so that it brings out much new phenomena and effects. Meanwhile, unlike the situation of many-cycle regime, in which case all processes are insensitive to the Carrier-Envelope Phase (CEP), in this circumstance the CEP is a key parameter for the driving field. As a result, the research on the CEP effects during the process of HHG driven by the few-cycle mid-infrared laser pulses has become one of the frontier hotspots among the researches on the intense laser-mater interactions. In this thesis, by choosing few-cycle mid-infrared laser pulses as the driving field, we investigate the CEP effects on the process of HHG, including the CEP effects on the spatial coherence of HHG and different phenomena of CEP effects on HHG driving by mid-infrared and near-infrared laser pulses. In addition, we propose a new method to measure the absolute energy of high harmonic energy. The main results and innovation points are listed as follows: 1. By choosing few-cycle mid-infrared laser pulses as the driving field, in the experiment we have observed the CEP effects on the spatial coherence of high harmonic signal for the first time. The degree of coherence varies with CEP periodically with a period of π. At the same time, as the harmonic orders increase, the extreme points on the curve of coherence degree vs. carrier-envelope phase shift toward the direction of carrier-envelope phase increasing. Through theoretical analysis, we find that the ionization induced frequency chirp plays an important role in the CEP effects on the spatial coherence. 2. By choosing mid-infrared few-cycle CEP stabilized laser pulses as the driving field for HHG process, different varying patterns of harmonic spectra with the CEP for three interaction gas mediums have been observed. Furthermore, by comparing our experiment results with the previous works driven by near-infrared laser pulses, different phenomena have been found. Through numerical simulation, we find that for the two different kinds of driving field, namely mid-infrared and near-infrared laser pulses, different kinds of electron trajectories contribute to the generation of high harmonics. 3. A power-meter for absolute energy measurement of high-order harmonic signal has been created. And it makes up the gap for the absolute energy measurement for high-order harmonic signal.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16867]
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	刁寒虎. 中红外周期量级激光脉冲驱动产生高次谐波中的载波-包络相位效应研究[D]. 中国科学院上海光学精密机械研究所. 2014.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。