光學同調斷層掃描(Optical coherence tomography, OCT) 有著高解析度、非侵入式即時成像的特點，可在不破壞樣品結構的情況下能在短時間內重建出掃描樣品的深度影像，目前廣泛運用於醫學方面的研究，如眼科、牙科和心臟外科等。OCT系統整體結構佔用較大的體積，本論文藉由絕緣體上覆矽(Silicon-on-insulator, SOI)技術作為縮小系統元件體積之應用，架設OCT時依實驗需求選擇適合的光源與元件，系統中光波導耦合器(Optical waveguide coupler)元件的功能將光源分成不同比例的光入射至樣品臂與參考臂，然而不同耦合器間有不同波長響應的平坦度(Flatness)，因為平坦度愈佳表示不同波長下分光比愈保持相同的光強度，平坦度愈差則會影響到影像的品質，透過理論驗證出波導耦合器的非平坦波長響應會降低系統感測靈敏度，耦合器寬頻響應對於OCT系統檢測性能是最重要的。
本論文中，首先架設光纖型SD-OCT系統，並量測系統的縱向解析度、橫向解析度與靈敏度，然後以不同波長響應平坦度的光波導耦合器各別取代SD-OCT系統中光纖耦合器部分進行實驗比較，觀察不同波長平坦度對於OCT系統靈敏度之影響，我們以標準差定義波長平坦度，實驗結果為若波長平坦度標準差越小則SD-OCT系統靈敏度越好，標準差越大則靈敏度下降。

Optical coherence tomography (OCT) owns high-resolution, non-invasive real-time imaging characteristics, and can reconstruct the depth of the scanned samples in a short time without damage. The OCT system is currently widely utilized in medical research such as ophthalmology, dentistry, cardiac surgery, etc., but suffers from the bulky size. The on-chip level OCT in silicon-on-insulator (SOI) platforms is then studied in this thesis for a small footprint application.
When setting up the OCT system, we should adopt the appropriate light source and components according to experimental needs. The optical waveguide coupler component in the system separates the light source into different portions of light, which will enter the sample and the reference arms, respectively. However, the non-flat wavelength response of waveguide couplers in OCT will degrade sensing sensitivity. The coupler broadband response is the current need to maintain the OCT performance.
In this thesis, a fiber based spectral-domain OCT (SD-OCT) will first be studied to accurately demonstrate the sensitivity, axial, and lateral resolutions. And then the silicon-wire couplers with different bandwidth flatness will replace the fiber coupler for OCT performance characterization. The experimental results demonstrate that the smaller the standard deviation of the wavelength flatness is, the better the SD-OCT sensitivity is, and the larger the standard deviation is, the lower the sensitivity is.

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