在本論文中，主要研究在1.55微米的通訊波長下的矽之電光調變器上。在研究中採用SOD熱擴散方法製作p+-i-n+結構式光調變器。使用SOD技術優點包含低成本且簡易化非常適合用來取代傳統離子佈植。除此之外，SOD技術也能相容於現今的CMOS製程。
在元件方面，利用分束傳播法設計並模擬一分二多模干涉架構下之馬赫-任德爾光調變器在Silicon-on-Silicon(SOS)基板上操作波於1.55μm波長，設計之後並製作。後來了解到，調變訊號藉由電流注入將導致兩個競爭調變機制互相作用，即熱光色散效應和自由載子消散效應。因此，兩者不同調變機制導致折射率變化量為反向。光波導調變器在不同調變長度下，靜態調變深度皆可高達100%，且本元件的頻率響應(f3dB)達336.5kHz。
此外，上述元件已被製做出來且製做 Silicon-on-Insulator (SOI)基板上，並與上述SOS基板做比較。實驗結果顯示在不同調變長度下，靜態調變深度皆可高達100%、達第一個π相位皆只需約0.2W的輸入功率且上升時間與下降時間已小於50 ns、截止頻率(f3dB)已大於5MHz。
最後，成功驗證出在SOI基板上製作1×2多模干涉架構下之馬赫-任德爾光調變器的調變機制為自由載子消散效應主導。

In this thesis, the attention is focused on an electrooptic Si-based modulator working at 1.55μm. The spin-on-dopant (SOD) thermal diffusion method was adopted to fabricate the optical modulator based on the p+-i-n+ structure. The advantages of using the SOD process include low cost and simplicity, and this very technique is therefore highly suitable to be used as an substitute for the conventional ion implantation. In addition, the SOD method is also compatible with the standard CMOS process.
On the device side, the 1 x 2 multimode interference (MMI) based Mach-Zehnder (MMI-MZI) modulators on silicon-on-silicon (SOS) substrates operating at 1.55μm were designed and simulated using the numerical beam propagation method (BPM), before subjecting the final design for device fabrication. It was later realized that the signal modulation by current injection led to two competitive modulation mechanisms in play, namely, the thermo-optic and plasma dispersion effects. Consequently, two opposing mechanisms would bring about the opposite refractive index changes. The aforementioned modulators with different modulation lengths being tested would eventually render the modulation depth closes to 100% and 3dB frequency response up to 336.5 kHz. Furthermore, the same devices mentioned previously were also fabricated and later tested on silicon-on-insulator (SOI) substrates for performance comparison. The experimental results demonstrate that a nearly 100% modulation depth was achieved for modulators with different modulation lengths, and only 0.2 W of input power was needed for devices to reach first phase shift. Finally, the devices on SOI substrates operated significantly faster in terms of signal modulation as the rise/fall times smaller than 50 ns and the 3dB cutoff frequency of greater than 5 MHz were measured, outright showing that the signal modulation was dominated by plasma dispersion effect.

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