緣層上覆矽波導具有低成本、高效率與高品質的特性，其與互補式金屬氧化物半導體的標準製程相容，更使得絕緣層上覆矽波導已使用於光纖通訊系統高密度分波多功(Dense Wavelength Division Multiplexing, DWDM)的核心元件中。在此波導中，矽與埋藏氧化層之間的高折射率差，使得元件線寬能微縮至次微米等級，因此以次微米矽線波導架構設計之高積體化與寬Free Spectral Range (FSR)的環形共振腔，也被提出於光通訊多功元件的應用。近年來在生醫方面，環形共振腔可應用於血糖作光波導外部覆蓋層，血糖濃度改變造成共振波長位移時進行感測，環形共振腔具有成本低廉、體積小、感測範圍大、可偵測多種溶液，且在不需要試紙的情況下作量測，因此極有商品化潛力。
此篇論文使用多模干涉器(Multimode Interference, MMI)作為環形共振腔的耦合器設計，MMI分光比對於波長與極化的不敏感特性，這特性使環形共振腔在生醫感測方面有更大效率的應用。同時在微影製程方面，傳統I-line曝光機就能達到理想MMI的長寬比，此有別於需要小於0.3-μm最小線寬的E-Beam曝光機之方向耦合器。之後我們使用變壓器耦合式電漿反應離子蝕刻機(Transformer Coupled Plasma REI,TCP-RIE)來蝕刻次微米矽線波導，藉由改變蝕刻反應氣體流量，使得波導垂直度大於85度與其側壁粗糙度小於10-nm，經實驗量得其傳播損耗約為15-dB/cm。
具有50:50分光比之MMI耦合器的環形共振腔，在實際量測結果得到在1550-nm波段的消光比為12-dB、品質參數為5740、FSR為0.55-nm，當覆蓋5g/dL的葡萄糖溶液，可測得共振波長變化為0.12-nm，如考慮可調式雷射之解析度為1-pm，理論的偵測極限是5.72×10-5 RIU(Refractive Index Unit)，同時其共振波長位移與血糖折射率變化的敏感度為161-nm/RIU。

Due to the advantages of silicon material on low cost, transparency in telecommunication wavelegnths, CMOS compatible processing, and the high index contrast for a small footprint, the silicon-on-insulator (SOI) platform is utilized to offer the potential of constructing and processing photonic integrated circuits on the massive electronics fabrication infrastructure. Ring resonator has been developed for its high density and wide free spectral range (FSR), thus utilized as the multiplexer in DWDM applications. In biosensing, the resonance wavelength shift induced by the refractive index change of sugar solution cladding could be detected by the ring resonator, which owns the properties of low cost, small foot print, wider sensing region, and test paper needless, thus with the potential for commercial applications.
In this thesis, the multimode interferometer (MMI), insensitive to the wavelength and polarization, was utilized as the coupling function in microring resonator for biosensing. In lithography process, I-line stepper could easily demonstrate the ideal critical dimension of 0.5 m. On the other hand, the directional coupler is requiring the E-Beam lithography to achieve the critical dimension of 0.3 m The vertical angle is above 85 degree, the sidewall roughness is less than 10 nm, and the propagation loss is characterized as 15 dB/cm.
The power splitting ratio of MMI was 50:50. The measured extinction ratio at 1550 nm wavelength and the quality factor were 12 dB and 5740, respectively. The FSR was 0.55 nm, and the phase shift was 0.12 nm while the microring resonator was cladded with 5g/dL sugar solution. If the resolution of tunable laser source is 1-pm, the detection limit could be shown as 5.72×10-5 RIU(Refractive Index Unit). The sensitivity of wavelength shift versus the glucose effective index change was 161 nm/RIU.

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