外部共振腔雷射擁有大波長調變範圍以及低線寬的優勢，近年被使用在許多光學系統上，成為熱門的研究主題。因為在遠距傳輸，光偵測以及光學雷達都需要低線寬和高輸出功率的雷射作為光源，很多研究團隊都想進一步提升外部共振腔雷射的線寬，波長調變範圍以及光功率。
為了實現穩定且擁有大範圍波長調變能力的可調式雷射，本論文利用模擬軟體來設計與優化以雙環諧振器作為外腔之可調式雷射，採用雙環諧振器提升共振腔長度，並選擇利用氮化矽波導平台製作降低傳播損失，以降低線寬。此雙環諧振器因半徑些微不同具有不同的自由頻譜範圍，將此雙環諧振器與增益晶片整合成可調波長雷射時，可以使用游標尺效應來增大可調波長範圍，但其波長調動的操作較為複雜，且牽涉的元件參數較多。
在模擬設計中會對於雙環諧振器外腔雷射的光學特性進行分析，像是環形諧振器的品質因子，細緻度和自由頻譜範圍以及其基本電性，並展示透過游標尺效應來達成波長調變的效果。經過模擬優化的雙環諧振器設計已下線利用氮化矽波導平台製作。
綜合上述模擬結果，以雙環諧振器作為外腔之可調式雷射波長調動範圍可以達到77.67奈米，旁模抑制比均大於35分貝，平均旁模抑制比為43.8分貝。

To realize a stable and widely tunable laser for applications in optical communication and sensing systems as a light source, this thesis utilizes simulation software to design and optimize a wavelength tunable laser with a dual-ring resonator as an external cavity. The dual-ring resonator offers different free spectral ranges. When integrating the dual-ring resonator with a gain chip to form a tunable laser, the Vernier effect can be employed to enlarge the wavelength tuning range. However, the wavelength tuning operation is complex and the device optimization involves multiple component parameters.

In the simulation design, the optical characteristics of the dual-ring resonator external-cavity laser are analyzed, including the quality factor, finesse, free spectral range, and basic electrical properties of the ring resonators. The effectiveness of wavelength tuning through the Vernier effect is demonstrated. The optimized design of the dual-ring resonator, achieved through simulation, has been tape-out for fabrication on a silicon nitride waveguide platform.

Based on the simulation results, the dual-ring resonator-based tunable laser achieves a wavelength tuning range of 77.67 nm, with a minimum side-mode suppression ratio (SMSR) exceeding 35 dB and an average SMSR of 43.8 dB.

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