隨著觀測的物體越小且越快速，對於使用於觀測的光源要求也更加嚴苛。目前為止，已經能運用高次諧波產生的線性偏振光源，進行材料結構、分子動態、激發探測實驗等等。但對於磁性材料、掌性化合物，相對於線極化光源，它們圓偏振的光源的反應更為靈敏。現今已有許多種方法能產生圓極化埃秒的脈衝，但到目前為止，各個方式所產生的脈衝還僅限於脈衝序列，相對於單發孤立脈衝，在激發探測實驗中會有較差的解析度。單發孤立的圓極化脈衝到目前為止僅只於理論計算，但在這篇論文中，我們成功產生世界上第一道單發孤立的圓極化脈衝，並驗證它的特性。
實驗中，我們重合兩道旋度相反的圓偏振固態白光雷射來產生高次諧波，並同時產生兩道旋性相反但旋度相同的圓偏振埃秒極紫外光，並藉由光譜儀量測到的超連續頻譜與場自相關干涉的結果做對照，驗證此光源波長是25〜40eV，時間上是孤立的單週期埃秒脈衝。此外，我們使用極紫外光的極化量測儀，它能同時分析光的旋性與旋度，證明我們產生的兩道光為+0.9與-0.93的左旋與右旋光。
我們進一步將此篇論文的技術延伸，藉由調整兩道固態白光雷射的旋度，產生任意旋度的孤立埃秒脈衝。

Along with the observation of smaller and faster objects, requirements of the light source used on observation are more demanding. So far, linearly-polarized high harmonics generation (HHG) has been used on many experiments such as resolving nanostructure of materials, molecules dynamics, pump-probe experiment and so on. However, for the magnetic materials and chiral compounds, they are very sensitive to circularly polarized light instead of linearly polarized one. Until now, there are few approaches to produce circularly-polarized attoseocnd (as) pulses, but all of them demonstrated so far are limited to as pulse trains, which limit the temporal resolution of the pump-probe experiments. Isolated circularly-polarized as pulses have been proposed in theory, but our team for the first time succeeded in producing isolated circularly-polarized as pulses and characterized its properties in details in this thesis.
In the experiment, we combined two counter-rotating circularly-polarized solid-state white light laser (MPContinuum / MPC) to produce HHG, which generated two counter-rotating polarized EUV beams with the same ellipticity simultaneously. By observing the supercontinuum spectrum, spanning from 25eV to 40eV, measured by EUV spectrometer and the trace of an E-field autocorrelation, indicating that those pulses are temporally isolated. Most importantly, we have built one EUV polarimeter which can unambiguously analyze the helicity and ellipticity of those two isolated as beams with ellipticity of +0.9 and -0.93 ( + : represents positive helicity, -：negative helicity). By further extending the non-collinear geometry for HHG, we are even able to convert the ellipticity of fundamentals to that of HHG, while keep the same conversion efficiency.

摘要 i
Abstract ii
Acknowledgements iii
List of Figures vi
Chapter 1. Introduction 1
1.1 High harmonics generation (HHG) 1
1.2 Motivation 4
1.3 Review of Circularly-Polarized High harmonics generation (CP-HHG) 5
Chapter 2. Theory 11
2.1 Non-collinear geometry (NCP-HHG) 11
2.1.1 Wave-mixing model of non-collinear geometry 12
2.1.2 Phase matching in NCP-HHG 16
2.2 NCP-HHG driven by single-cycle pulse 18
2.3 Polarization-Gating effect in NCP-HHG 19
Chapter 3. Experiment 26
3.1 Light source 27
3.1.1 Multiple-plates continuum(MPC) 27
3.1.2 PG-FROG and compressor 28
3.1.3 Non-collinear HHG 31
3.2 Spectrometer 35
3.2.1 Experimental set up 35
3.2.2 Linearly polarized continuous spectrum 38
3.2.3 Continuous spectrum of isolated, circularly-polarized pulses 39
3.2.4 Delay dependence of spectrum 40
3.2.5 Dispersion dependence of spectrum 41
3.3 Autocorrelator 42
3.3.1 Calibration of autocrrelator 43
3.3.2 Fourier transformation spectrum 44
3.4 Polarimeter 46
3.4.1 Experimental set up 46
3.4.2 Theory and analytical procedure 48
3.4.3 Measuring linearly-polarized attosecond pulses 51
3.4.4 Circularly-polarized attosecond pulses 52
Chapter 4. Conclusion and perspective 55
Reference 58

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