角度解析光電子能譜（ARPES）是研究固態材料電子能帶結構的有力工具，它提供了新型材料的電子能帶結構在能量及動量方面的資訊。最近，ARPES與超快雷射的結合開闢了新的領域，用於捕獲光激發電子的動態行為，且提供能量、動量和時間相關的訊息。
本論文包括兩部分：在台灣國家同步輻射研究中心（NSRRC）所開發之基於高次諧波產生（HHG）光源的時間及角度解析光電子能譜（Tr-ARPES）系統以及其在石墨中熱電子的超快動力學之研究。 通過多重薄片展頻連續譜技術（MPC）對雷射脈衝進行壓縮，我們有效地提高了高次諧波產生光源的效率。此外，通過使用離面安裝光柵 (off-plane mounted grating)，使該系統達到了約165飛秒 (fs) 的時間解析度和 180毫電子伏特 (meV) 的能量解析度，且光子通量達到接近每秒 1011 個光子。 並且，通過時間及角度解析光電子能譜實驗，我們研究光激發後石墨中電子分佈的超快響應。 這些實驗揭示了非熱電子存在於非微擾激發光能量密度條件之下，且其壽命為 284 fs。此外，我們還揭示了在有能帶間隙的 H 點和無能帶間隙的 K 點中，其熱電子弛豫動力學表現的差異。

Angle-resolved photoemission spectroscopy (ARPES) is a powerful tool for studying the electronic structure of solids, it provides direct insight to the electronic structure of novel material with energy and momentum information. More recently, the combination of ARPES with ultrafast lasers has opened up new frontiers for capturing the dynamics of photo-excited electrons, providing the energy, momentum, and time information.
This thesis comprises two parts: The development of the high-order harmonic generation (HHG) light source-based time-resolved ARPES (Tr-ARPES) system in National Synchrotron Radiation Research Center (NSRRC), Taiwan, and the investigation of hot electron dynamics in graphite using the Tr-ARPES system. By employing the multi-plate continuum (MPC) technique for post-compression of laser pulses, we effectively enhance the efficiency of high-order harmonic generation (HHG). Furthermore, with the utilization of an off-plane mounted grating, the system achieves a temporal resolution of 165 fs and an energy resolution of 180 meV, with a photon flux reaching close to 1011 photons/s. Through the Tr-ARPES experiment, we can investigate the ultrafast response of the electron distribution in graphite following photoexcitation. These experiments reveal the existence of non-thermal electrons with a lifetime of 284 fs under non-perturbative pump fluence conditions. Additionally, we uncover the disparity in relaxation dynamics of hot electrons at the gapped H point and gapless K point.

Acknowledgement I
Abstract II
摘要 III
List of Figures VII
List of Tables XV
Chapter 1 Introduction 1
Chapter 2 Backgrounds 5
2.1 Angle-resolved Photoemission Spectroscopy 5
2.1.1 Photoemission Process 7
2.1.2 Basics Principle of Angle-resolved Photoemission Spectroscopy 10
2.2 High Harmonic Generation Light Source 20
2.2.1 Three-Step Model 21
2.2.2 Macroscopic Phase Matching 26
Chapter 3 Tr-ARPES Apparatus 32
3.1 Overview 32
3.2 The Probe Line 38
3.2.1 Multi-plates Continuum Technique 39
3.2.2 The HHG Beamline 44
3.2.3 Off - planed Mounted Grating 47
3.3 The Pump Beam 53
3.4 System Characterization and Stabilization 55
Chapter 4 Ultrafast Dynamics of Hot Electrons in Graphite 65
4.1 Introduction: Graphene and Graphite 65
4.2 Ultrafast Hot electron Dynamics in graphite 80
4.2.1. Quasi-equilibrium and Non-thermal electrons 82
4.2.2. Relaxation dynamics of hot electrons 87
4.2.3. Comparison with the equilibrium high-temperature ARPES data 91
4.2.4. Direct View of kz-dependent hot electron dynamics 94
4.3 Summary 102
Chapter 5 Conclusion 104
References 107

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