臺灣博碩士論文加值系統

本論文使用stimulated Raman adiabatic passage (STIRAP)的概念設計出非對稱絕熱耦合器的結構，並且將此結構應用在鈦擴散式鈮酸鋰波導上，作為偏振分光器。而此設計是用兩段的結構，將兩個不同的偏振光分開，已達成偏振分光器的效果。在模擬上，先針對不同結構的情況去比較，以1550 nm為中心波長，使TE、TM偏振都能達到良好的效果，再將結果結合，進行大範圍波長的模擬，來達成寬頻分光器的效果，最後在對pump的偏振光進行模擬，以波長775 nm為主，兩個偏振的pump光只會從C出口輸出。而本論文利用模擬結果的結構，實際製作出寬頻偏振分光器的晶片，並加以量測。
在本實驗的製程是以黃光微影以及高溫擴散的方式，製作出鈦擴散式鈮酸鋰波導非對稱絕熱耦合器之寬頻偏振分光器，最後進行兩個端面的拋光，來完成晶片的製作。
在量測的結果上，在波長範圍1500 nm到1600 nm，兩個偏振都有良好的分光比，大約在95%到99%之間，TM偏振的寬度在120 nm，TE偏振的寬度在130 nm，都有著很寬的範圍。

In this study, the structure of asymmetric adiabatic coupler (AAC) is designed using the concept of Stimulated Raman Adiabatic Passage (STIRAP), and applied it on the lithium niobate(LiNbO3) with the titanium diffused waveguides to become a polarization beam splitter. We designed the structure into two parts to split TE and TM polarization. Our goal is to achieve the broadband polarization beam splitter by using a two-stage structure to separate two different polarized lights. Before the fabrication process, we do the simulation part. In the simulation process, first step we use 1550 nm as the center wavelength to simulate TE and TM polarization in different structures. Second step, based on our previous simulation, we apply an adiabaticity engineering method to optimize the waveguide system configuration to achieve a broadband polarization beam splitter. Finally, we use a TE-polarized 775 nm laser as the pump to examine the structure to make sure the pump will be spatially filtered from the cross-polarized signal and idler. Furthermore, we fabricated such an AAC chip to measure the experimental result.
We used the standard lithography process and titanium diffusion process to fabricate the AAC chip in a 51 mm long, 25 mm wide, and 0.5 mm thick LiNbO3 crystal.
In the measurement result, we had a good-fitting result with the simulation process. It can be found a bandwidth of >120 nm can be achieved in this unique Ti:LiNbO3 polarization beam splitter at a power splitting ratio of >95% for both polarization modes, which is to the best of our knowledge the broadest bandwidth ever reported in integrated optical LiNbO3 polarization beam splitters.

目 錄
摘要 ii
Abstract iii
致謝 iv
目 錄 v
表目錄 vi
圖目錄 vi
一、 緒論 1
1-1 積體光學簡介 1
1-2 定向耦合器(Directional coupler)的簡介與發展 1
1-3 絕熱耦合器(Adiabatic coupler)的簡介 2
1-4 研究動機 6
1-5 內容概要 8
二、 實驗原理 9
2-1 拉比共振(Rabi oscillation)[14] 9
2-2 Stimulated Raman adiabatic passage(STIRAP)[14-15] 11
2-3 三波導耦合方程式[8,14,17] 13
2-4 三斜波導耦合方程式 17
2-5 錐形波導耦合方程式 18
三、 模擬結果與晶片製作 21
3-1 元件設計 21
3-2 元件模擬 25
3-3 鈦擴散式絕熱耦合器製程 27
四、 實驗結果與分析 33
4-1 AAC特性量測 33
4-2 耦合特性量測結果分析 39
五、 結論與未來展望 44
5-1 結論 44
5-2 未來展望 46
參考文獻 49

表目錄

▲表1　波導設計參數 23
▲表2　折射率比(〖∆n〗_TM⁄〖∆n〗_TE )的量測結果(表中x：為未進行製作及量測) 24

圖目錄

▲圖1 三波導耦合器的輸出功率以及波導出口的光強度，輸入光分別從(a)左側波導(b)中央波導(c)右側波導輸入[7] 4
▲圖2　(a)三波導結構示意圖與入射光位置 (b)傳遞距離與光強度關係(波導1對應I1以此類推，入射光導入波導3) [8] 4
▲圖3　多波導絕熱耦合器結構示意圖 [9] 5
▲圖4　(a)實驗量測結果(b)實驗模擬結果(c)波導中光強度模擬結果[9] 5
▲圖5 鍾宏彬博士實驗的元件設計[13] 7
▲圖6　三能階系統示意圖[14] 11
▲圖7　(a)泵浦雷射P和斯托克雷射S的拉比頻率在時間上疊合程度的示意圖(b)能階ψ1、能階ψ2與能階ψ3粒子數對應時間的示意圖[15] 13
▲圖8　三波導結構示意圖 16
▲圖9　三斜波導結構示意圖 18
▲圖10　錐形波導結構示意圖 19
▲圖11　傳播常數β1與β3對位置的關係圖 19
▲圖12　(a)元件左半部錐形波導設計(b)元件右半部三斜波導設計 22
▲圖13　元件結構設計圖 23
▲圖14　高溫擴散的參數 24
▲圖15　用prism coupler量測單模波導結果 24
▲圖16　左半部模擬結果(TM偏振) 25
▲圖17　(a)用TM偏振入射光的模擬結果(b)用TE偏振入射光的模擬結果 25
▲圖18　以TM、TE偏振的pump為入射光的模擬結果 26
▲圖19　以波長775nm的TM(左)、TE(右)偏振的pump為入射光的模擬結果 26
▲圖20　鈦擴散波導製作流程圖 27
▲圖21　黃光製程後的波導線寬及波導間距(TM偏振出光位置) 29
▲圖22　黃光製程後的波導線寬(TE偏振分光位置) 29
▲圖23　掀離後的波導線寬及波導間距(TM偏振出光位置) 30
▲圖24　掀離後的波導線寬(TE偏振分光位置) 30
▲圖25　掀離法後晶片結果圖 31
▲圖26　鈦擴散波導結構圖(TM偏振分光處) 31
▲圖27　鈦擴散波導結構圖(TE偏振出光處) 32
▲圖28　高溫擴散後晶片實圖 32
▲圖29　AAC量測架構圖 33
▲圖30　入射光由C波導輸入，量測各個出口L、C和R的輸出光功率 34
▲圖31 波導編號13-8-4 TE偏振光場分布 35
▲圖32 波導編號13-10-5 TE偏振光場分布 35
▲圖33 波導編號14-9-6 TE偏振光場分布 36
▲圖34 波導編號15-9-6 TE偏振光場分布 36
▲圖35 波導編號15-8-7 TE偏振光場分布 37
▲圖36 波導編號14-8-8 TE偏振光場分布 37
▲圖37 波導編號14-9-6 TM偏振光場分布 38
▲圖38 波導編號14-8-8 TM偏振光場分布 39
▲圖39 TM偏振光模擬結果圖 40
▲圖40 TM偏振光L、R和C出口模擬與量測結果疊合圖 40
▲圖41 TM偏振光1500 nm-1640 nm L、R和C出口模擬與量測結果疊合圖 41
▲圖42 TE偏振光模擬結果圖 42
▲圖43 TE偏振光L、R和C出口模擬與量測結果疊合圖 43
▲圖44 TE偏振光1500nm-1640nm L、R和C出口模擬與量測結果疊合圖 43
▲圖45 ∆n對應波長的示意圖 45
▲圖46 將∆n進行調整後，對應波長的示意圖 45
▲圖47 PAC的結構設計與模擬 47
▲圖48 衰減係數與TE和TM波的緩衝層厚度 47
▲圖49 金和鋁的厚度對應TM偏振光的衰減係數 48

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