2010年，Nature Photonics的Focus專欄推出一系列關於矽光子學的相關文章，包括矽鍺光偵測器、矽雷射、非線性現象與Intel所推出的LightPeak相關介紹，足見矽光子學在光通訊元件領域舉足輕重。我們利用絕緣層上覆矽蝕刻矽波導，是由於矽與二氧化矽的高折射率差異可有效達成光路集積化的目的，加上便宜、65奈米解析即可的製程條件與相容於CMOS半導體技術，使得矽光子學的研究極具商業價值。
儘管單晶矽屬於等向性材料，但高折射率差異與次微米結構使得波導因幾何形狀產生高的相/群雙折射效應與色散，對於陣列波導光柵、環型共振腔等對波長敏感之元件，必須嚴肅面對其波導的設計。
本論文中首先探討各種結構之次微米矽線波導有效折射率的計算；我們利用套裝軟體RSoft中的Mode Solver作計算；在計算中同時考慮Sellmerier Equation波長對材料折射率，與波導幾何形狀的影響。由於群折射率與色散分別為有效折射率的一次與二次微分，微小的誤差會造成微分後極大的影響，參考論文提出，使用RSoft套裝軟體設定在20x20x20nm的解析，收斂容忍度在10^-9以下最為理想。由上述設定結果進而推算群折射率、相/群雙折射效應與色散。此結果與寬5μm，高5μm蝕刻2.5μm之矽波導實驗數據作比較，雙折射實驗值為-7.9*10^-4、模擬值-2.48*10^-4與色散實驗值-900ps/nm-km模擬值-854.515ps/nm-km誤差為5%。
色散的測量與先前矽波導(W5H5h2.5)的量測方式同為干涉法，極低的色散無法用干涉法求出色散值。比較其干涉線寬，覆蓋二氧化矽之波導半高寬寬度為74μm，去除覆蓋層之波導半高寬寬度則為41μm，相較於光纖線寬83μm窄上許多。推測是由於微矽線波導披覆300nm之二氧化矽作為保護層，80MPa應力所造成的次微米結構折射率變化所影響。
實驗架構利用低同調干涉儀測量次微米矽線波導之群雙折射效應，由於微矽線波導不適合使用物鏡作側壁耦光，因此吾人改良極化控制系統，該系統寬頻譜光源之隔離度可達26dB，具高穩定度與重複性。並以Intel設計之二氧化矽波導作為樣本證明該波導之低雙折射效應。此系統用於次微米矽線波導之測量值僅-0.0005，與模擬值-0.346差異甚大，但吾人於波導上覆蓋5%、10%與20%之葡萄糖水以模擬不同血糖濃度的折射率，並成功測量出其相位變化，代表該架構確實可分析出折射率之微小變量，此結果將有助於未來生醫感測領域之研究。

In 2010, a series of editorials about Silicon Photonics has been published in “Focus” column of Nature Photonics, which mentioned the most popular issues including Ge-on-Si photodetectors, silicon lasers; nonlinear effects and the introduction of Light Peak developed by Intel. It proves Silicon Photonics will hold the balance of power in the optical communications. We utilize silicon-on-insulator platform for highly integrated photonics devices because of high refractive-index contract between silicon and silicon dioxide layers. Moreover, low cost, 65 nm resolutions in lithography, and complementary metal-oxide-semiconductor (CMOS) process compatible makes it full of commercial benefit.
Although single crystalline silicon is an isotropic material, but high refractive-index contract and sub-micron scale makes silicon photonic wire geometric shapes difference would induce highly phase/group birefringence and dispersion. Wavelength sensitive devices like arrayed waveguide grating or ring-resonator, effective indices change will lead crucial impacts on devices design.
In this thesis, the effective indices calculations for each sub-micron photonic wire structure is discussed at beginning; we utilize RSoft package software to estimate effective indices, and considering both waveguide geometric shapes differences and the material indices changes discussed from Sellmerier Equation. Since group indices and dispersion are related to once and twice differential values of effective indices. A tiny estimate inaccuracy induces large deviation. Reference shows that RSoft package software with 20x20x20nm grid size and convergence tolerance below is the most suitable settings. Furthermore, follow those program settings to estimate the group indices, phase/group birefringence and dispersion. Compared with the waveguide of width 5μm, height 5μm, and slab high 2.4μm (W5H5h2.4) experiment results, birefringence is -7.9*10^-4, and simulation value is -2.48*10^-4. Dispersion experiment result is -900ps/nm-km and simulation value is -854.515ps/nm-km. The deviation is about 5%.
To determine the silicon wire dispersion, the interferometric methods had been utilized for W5H5h2.4 waveguide and had been demonstrated successfully, extremely low dispersion cannot obtained by using interferometric methods. The interference pattern line width of silicon wire with and without silica cladding is 74μm and 41μm, both structures are narrower than pure fiber which is 83μm. Infer that the effective index changes induced by 300nm thickness and 80MPa stress of silica cladding may be the possible reason.
Optical low-coherence interferometer (OLCI) had been utilized to obtain group birefringence of silicon wire. Since silicon wire is not suitable for objective surface coupling, we had improved the polarization control system. With high stability, high repeatability and high isolation up to 26dB above, this system also measured birefringence by using Intel’s low birefringence silica waveguide. The silicon wire group birefringence measurement result only -0.0005, is a large deviation compared with simulation result -0.346. However, we use sugar solution of 5%, 10% and 20% as the silicon wire cladding, and successfully measured the phase differences. It proves that the tiny indices variation can be analyzed by OLCI system, and that will be contributive to study for biomedical sensing in the future.

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