本實驗利用大孔徑光導天線激發兆赫波，並用自由空間電光取樣方法偵測兆赫波的時域訊號。我們分別對鎵石榴石陶瓷（Re3Ga5O12）與複合式鈣鈦礦陶瓷（xLa(Mg1/2Sn1/2)O3-(1-x)La(Mg1/2Ti1/2)O3）的介電特性進行研究；其中鎵石榴石陶瓷之A-site元素由不同的稀土族元素（Re = Nd、Sm、Eu、Dy）所置換，而複合式鈣鈦礦陶瓷之x代表錫原子的濃度（x = 0.00、0.25、0.50、0.75、1.00）。這兩組樣品之前都測過微波的拉曼散射光譜（Raman）及紅外光譜（Infrared），但分析後微波的介電損失都比紅外光譜的線性外插結果來的高一些，初步推測是樣品在製備過程中，晶粒與晶粒之間有一些孔洞、結構非有序或二次相產生，而造成樣品的非本質損失（Extrinsic loss）。因此我們利用兆赫波來測量樣品在0.1 ~ 1.0 THz範圍內的介電損失，發現兩組樣品在兆赫波段的數據都沒有吻合紅外光譜線性外插曲線的值，即驗證了這兩系列樣品在製備過程中或許都有一些孔洞、結構非有序或二次相而造成非本質損失的特性。

Coherent THz time domain spectroscopy was used to measure the dielectric proper-ties of Re3Ga5O12 (Re = Nd、Sm、Eu、Dy) garnet ceramics and xLa(Mg1/2Sn1/2)O3 - (1-x)La(Mg1/2Ti1/2)O3 (x = 0.00、0.25、0.50、0.75、1.00, in which x represents different concentration of Sn atoms) perovskite ceramics. The large-aperture photoconductive antenna was used to generate terahertz (THz) waves, then using the free-space elec-tro-optic sampling method to detect THz wave signals. Both Re3Ga5O12 garnet and xLa(Mg1/2Sn1/2)O3-(1-x)La(Mg1/2Ti1/2)O3 perovskite ceramics have been characterized by Raman and Infrared (IR) reflectivity spectroscopy before, however, the dielectric loss at microwave range is slightly higher than that predicted by the IR measurement. It is preliminarily induced that the extrinsic losses of samples in the process of sample preparation were caused by porosity, disorders and secondary phase generation at grain boundary of crystal grains. Therefore, we used THz spectrum to obtain the measured dielectric losses of both aforementioned ceramics in the range of 0.1-1.0 THz, and we found that the dielectric losses of both samples at THz spectrum also did not match the prediction made by IR spectroscopy. As a conclusion, these two series ceramic samples have the extrinsic losses that predominantly come from the porosity, disorders and secondary phase at grain boundary of crystal grains during sample mak-ing process.

Chapter 1
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Chapter 2
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Chapter 3
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Chapter 4
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附錄
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[2] 許聖賢, “Probing the Thin Films via Terahertz Spectroscopic Technique,” 國立台灣海洋大學光電科學研究所碩士論文（2005）