在積體光路元件中，環型共振腔(ring resonator)具有選擇波長的功能，因此被廣泛的應用於許多光學器材中，目前常作為環型共振腔的材料為矽(silicon, index=3.4)和氮化矽(SiN, index=1.6~2)，其共振波長和共振腔的等效折射率有關，而因向列型液晶(nematic liquid crystal)擁有相位調製的能力，故常被應用於製作可調式環型共振腔，藉由電控或光控調諧共振波長。但是向列型液晶為各方異向性(anisotropic)的光學材料，在作為共振腔的包覆層時很容易造成散射損失，且反應速度慢，影響到波長調控的品質。 本實驗利用藍相液晶製作環型共振腔的包覆層，實現快速響應且低損耗的可調式環型共振腔。藍相液晶為光學上各方同向性，且因其結構的特性擁有快速的反應時間，而氮化矽波導的折射率較矽波導低，因此在作為可調式共振腔時，藍相液晶受電場引致的折射率差可以更有效率的改變共振波長。由實驗結果得知，我們製作的藍相液晶環型共振腔的調控範圍達2.85nm，而在電壓低於140V以下時，反應時間為次毫秒等級(sub-millisecond)，且由頻譜得到的品質因數(Q-factor)可得知此元件具有低損耗的優點。

Ring resonators usually made of SiN (refractive index=1.6~2) or silicon (refractive index=3.4) possess wavelength selectivities and have been widely used in integrated optical circuits. The resonant wavelengths of ring resonators can be tuned by varying the effective index of ring resonators. Due to the nematic liquid crystals can function as phase modulation materials, they can be employed as the cladding of ring resonators to provide high tunability. However, the scattering loss raises due to the lower order of the nematic liquid crystal alignment. In addition, the response time is long for the nematic liquid crystal, which reduces the applications of the ring resonators. In this study, we propose a tunable low-loss SiN ring resonator with a blue phase liquid crystal (BPLC) cladding. The BPLC is an optically isotropic material with short response time. By apply an electric field, the Kerr effect would be induced due to the local reorientation, lattice deformation and phase transition of the BPLC, leading to the effective index variation and the resonant wavelengths shift of ring resonators. Due to the refractive index of SiN is close to the BPLC, a very wide tuning range of 2.85 nm for TM mode can be achieved. In addition, the response time of the ring resonators with BPLC cladding can be kept at sub-millisecond level as the voltage is smaller than 140V. The proposed BPLC ring resonator also demonstrate a high Q-factor owing to the low scattering loss of the BPLC.

中文審定書 i
英文審定書 ii
誌謝 iii
中文摘要 iv
Abstract v
目錄 vi
圖目錄 viii
表目錄 x
第一章 緒論 1
第二章 簡介 3
2-1 液晶簡介 3
2-1.1 何謂液晶 3
2-1.2 液晶的分類 4
2-2 液晶的物理特性 8
2-2.1 向列型液晶的物理特性 8
2-2.2 雙折射性 8
2-2.3 介電異向性 11
2-2.5 液晶的連續彈性體理論 12
2-2.5 液晶分子排列的秩序性參數 13
2-2.6 溫度變化對液晶分子的影響 14
2-3 藍相液晶 15
2-3.1 藍相液晶的特性 15
2-3.2 藍相液晶結構介紹 16
第三章 理論介紹 18
3-1 環型共振腔簡介與理論介紹 18
3-1.1環型共振腔簡介 18
3-1.2 環型共振腔的共振條件 19
3-1.3自由光譜範圍 20
3-1.4 品質因數和半高寬 20
3-2 高分子穩定型藍相液晶理論 21
3-2.1高分子穩定型藍相液晶 21
3-2.2藍相液晶在電場下的反應 22
3-3 藍相液晶的Kerr effect 23
第四章 實驗過程與方法 25
4-1 材料介紹 25
4-2 電控環型共振腔製作 29
4-2.2 高分子穩定型液晶元件 32
4-3 實驗量測裝置 33
第五章 實驗結果與討論 35
5-1 藍相液晶於環型共振腔之觀察與分析 35
5-1.1 高分子穩定型藍相液晶於環型共振腔溫度範圍觀察分析 35
5-1.2 高分子穩定型藍相液晶外加電場觀察分析 36
5-2 BPLC ring resonator 穿透頻譜之電控分析 37
5-3 BPLC ring resonator 反應時間之量測與分析 42
5-4 BPLC ring resonator 穩定度測試與分析 47
第六章 結論與未來展望 54
參考文獻 56

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