臺灣博碩士論文加值系統

本論文是以SOI( Silicon on Insulator )為基板材料的光波導環形共振腔之非線性現象為研究主題。在環形共振腔中藉由改變環形波導的半徑與和傳輸波導的間距能使共振頻譜達到高消光比、窄線寬的濾波器。當消光比高、線寬窄時，代表環形波導內儲存相當高密度的能量。當能量輸入越高時，環形波導內的能量會使材料產生雙光子吸收(Two photon absorption)，而雙光子吸收會造成額外的自由載子釋放出來，進而使熱累積在波導內。在這三個現象，雙光子吸收、自由載子吸收(Free carriers absorption)、熱效應的影響下造成波導非線性的折射率變化，此時共振頻譜會不對稱並產生位移。另外，當入射波長從短波長往長波長移動與從長波長往短波長移動其穿透共振頻譜會有雙穩態(Bistability)的現象。因此可藉由波長的位移量與雙穩態去判斷此非線性現象的強弱。
在本論文分成三個部分，第一部分是披覆層為空氣，利用矽波導與兩旁包覆層的二氧化矽本身的雙光子吸收得到波長的位移量與雙穩態現象做為參考值。其波長位移量在半徑2.5μm、5μm與10μm下分別約為0.6nm/mW, 0.26nm/mW and 0.14nm/mW。為了提升非線性熱光效應，本論文將改變披覆層的材料來達到效果。第二部分是把石墨烯當作披覆層，並進行紫外光與臭氧之光反應表面處理(UV/O3 ozone)將石墨烯氧化成氧化石墨烯，在氧化時間增加的時候，損耗會因氧化的程度而開始減少，從9dB/mm下降至1dB/mm，波長位移量也逐漸的上升。第三部分則是將石墨烯換成由氧化石墨烯水溶液塗佈形成的薄膜，在塗佈之後利用臭氧反應表面處理將氧化石墨烯再次氧化蝕刻。此時，在第二部分及第三部分的波長位移量可達到約1.2nm/mW, 0.9 nm/mW and 0.4 nm/mW，是原來的兩倍之多。兩種不同披覆層材料在雙穩態的反應速度上皆有其優缺點，可以根據未來應用方面的不同選擇適性的方法。

This thesis focuses on the nonlinear effects of the Si micro-ring resonators on silicon-on-insulator platform. A high extinction ratio and narrowband filter can be achieved by using a high-quality-factor micro-ring resonators, which typically has a small radius and a wider gap between the ring and the straight bus waveguide. As we look for higher quality factor, the storage of photon energy inside the ring is also enhanced, leading to stronger nonlinear effects. Such a field enhancement in the ring resonator gives rise to two photon absorption (TPA) and its induced free carrier absorption effect, all leading to a nonlinear photo-thermal phenomenon. Due to these effects, an increase in input optical power of micro-ring resonator would result in an asymmetric resonance dips, wavelength shift, and bistability in its transmission spectra. The reference micro-ring resonators with an air top-cladding are characterized to exhibit a wavelength shift of 0.6 nm/mW, 0.26 nm/mW, and 0.14 nm/mW, respectively, for a radius of 2.5 μm, 5μm, and 10 μm. We anticipate to enhance the photo-thermal nonlinearity by depositing a graphene oxide layer atop the air-clad micro-ring resonators. The graphene oxide thin film can be obtained by either converting from a monolayer pristine graphene via ultraviolet ozone treatment or by spin-coating chemically-exfoliated graphene oxide. Experimental results reveal a two-time enhancement in wavelength shift of 1.2 nm/mW, 0.9 nm/mW and 0.4 nm/mW, respectively, from graphene oxide covered micro-ring resonators having a radius of 2.5 μm, 5μm, and 10 μm.

論文審定書 i
中文摘要 ii
Abstract iii
第一章 緒論 1
1.1. 矽光子技術 1
1.2. 研究動機 2
1.3. 論文大綱 3
第二章 環形共振腔 5
2.1. 環形共振腔之原理 5
2.1.1. 模態耦合理論 6
2.1.2. 全通式/塞取式(add/drop)濾波器理論模型 8
2.1.3. 自由頻譜範圍 11
2.1.4. 光學損耗與品質因子 12
2.2. 數值模擬方法-有限時域差分法( FDTD ) 13
第三章 石墨烯及非線性現象原理 15
3.1. 石墨烯與氧化石墨烯之介紹 15
3.1.1. 石墨烯與氧化石墨烯特性 15
3.1.2. 石墨烯與氧化石墨烯之製備 17
3.2. 非線性現象原理 18
3.2.1. 飽和吸收(Saturable absorption) 19
3.2.2. 雙光子吸收 (Two photon absorption) 20
第四章 量測系統架構 25
4.1. 波長掃描量測系統 25
第五章 實驗結果與討論 27
5.1. 環形共振腔以空氣作為披覆層之量測分析 27
5.1.1. 環形共振腔在不同半徑下的線性量測結果 27
5.1.2. 環形共振腔在不同半徑下的非線性量測結果 30
5.2. 環形共振腔以單層石墨烯於不同氧化時間下作為披覆層之量測分析 32
5.2.1. 試片於不同氧化時間下之頻譜量測 33
5.2.2. 試片於不同氧化時間下之光學特性分析 36
5.2.3. 試片於不同氧化時間下之非線性頻譜量測 38
5.3. 環形共振腔以氧化石墨烯作為披覆層之量測分析 40
5.3.1. 氧化石墨烯與單層石墨烯之比較 41
5.3.2. 試片之光學特性分析 41
5.3.3. 試片之非線性頻譜量測 43
5.4. 不同披覆層材料下之雙穩態現象 44
第六章 總結 46
未來工作 48
參考文獻 49

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