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Title: | 發展寬頻光學和頻干涉光譜技術用以研究手性拓樸半金屬電子共振 Development of Broadband Heterodyne Optical Sum-Frequency Spectroscopy for Investigating Electronic Resonances in Chiral Topological Semimetals |
Authors: | 劉思彤 Si-Tong Liu |
Advisor: | 蘇國棟 Guo-Dong J. Su |
Keyword: | 非線性光學,和頻產生,外爾半金屬,矽化鈷,飛秒雷射, nonlinear optics,sum-frequency generation,Weyl semimetal,cobalt silicide,femtosecond laser, |
Publication Year : | 2022 |
Degree: | 碩士 |
Abstract: | 最近在具有偏心晶體結構(acentric crystal structure)的外爾半金屬中發現了許多奇異且有趣的量子現象。自旋—軌道耦合與反轉對稱性破缺使得外爾點周圍的能態有自旋極化,並且外爾錐的自旋紋理與外爾點的手性相關。奇特的自旋紋理使外爾半金屬擁有新穎的線性光學性質以及獨特的非線性光學響應。例如,最近在TaAs和CoSi等外爾半金屬中發現了巨大二次諧波產生和光伏效應。這些特性在許多應用中都提供了新的可能性,例如高靈敏度的兆赫波光電探測器。目前該研究領域面臨的主要挑戰是理解電子在單一外爾錐的帶間躍遷引起的非線性光學特性。
在此工作中,我們的目標是於紅外光頻段內進行非線性光譜研究,並藉此了解由單一外爾錐內的的電子躍遷所決定的二階極化率。 基於上述的動機,我們設計了一個寬頻光學和頻干涉光譜量測系統,並借助此裝置在1200-8000cm-1間量測出複數形式的二階非線性光學極化率。本論文將討論我們的光譜學發展,並且應用此光譜系統在寬頻譜範圍中揭示矽化鈷(Cobalt Silicide)的二階章量極化率數值。 Many exotic phenomena in Weyl semimetal with acentric crystal structure have been discovered recently. Due to spin-orbit coupling and inversion symmetry breaking, the states around the Weyl node are spin-polarized, and the spin-texture of the Weyl cone is related to the chirality of the Weyl node. The peculiar spin-texture leads to novel linear optical properties and unusual nonlinear optical responses of Weyl semimetals. For example, giant second harmonic generation and linear photogalvanic effect have been recently discovered in TaAs and CoSi Weyl semimetals, which offers new opportunities for a variety of applications, such as high-sensitivity terahertz photodetectors. The major challenges in this research field are the understanding of the special nonlinear optical properties for the interband transition of an electron across a single Weyl cone. Here we aim to conduct nonlinear spectroscopy research in the infrared range to examine the second-order susceptibilities dictated by interband electronic transition across the Weyl cone. We design a broadband heterodyne sum-frequency spectroscopic setup for deducing the complex second-order nonlinear optical susceptibility with an input beam scanning between 1200 and 8000 cm-1. This thesis will discuss our spectroscopy development and its application in revealing the non-vanishing second-order tensor elements of cobalt silicide. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/87629 |
DOI: | 10.6342/NTU202210016 |
Fulltext Rights: | 同意授權(限校園內公開) |
metadata.dc.date.embargo-lift: | 2025-12-31 |
Appears in Collections: | 光電工程學研究所 |
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ntu-111-1.pdf Restricted Access | 2.75 MB | Adobe PDF | View/Open |
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