雷射光學的發展提供了高強度的光源，使得非線性光學也得以實際使用到許多研究及日常生活中。而微型化後的積體雷射元件，更是在多種領域中廣泛的發展，例如藍光雷射可應用於生物醫療、光儲存與資訊讀寫、雷射列印以及高解析度印刷器的發展。
鎂摻雜鈮酸鋰晶體具有高非線性係數以及電光係數且大幅減少了光折變損害，適合應用於和頻以輸出藍光窄頻光源，本研究即在鎂摻雜鈮酸鋰晶體上製作軟質子交換波導與準相位匹配結構，針對波長976nm輸入至488nm藍光輸出的二倍頻轉換進行優化，目的使轉換效率接近理論值。造成實驗和理論轉換效率差異原因有三，一、波導的耦合條件和基頻光976nm的耦合條件不匹配，以至於耦合損耗過大。二、波導中等效折射率造成準相位匹配週期的差異。三、基頻和倍頻模態在波導疊加積分不足。
首先，本論文使用模場直徑量測法量測出軟質子交換通道式波導的基頻光基模模場分布，取得了實驗上通道式波導的耦合條件。再者，進行等效折射率分布量測，得到976nm基頻光基模在通道式波導內的等效折射率，配合稜鏡耦合器量測並計算出波導內976nm二倍頻轉換所需週期基模轉基模週期𝛬0−0=4.3𝜇𝑚與基模轉第一高階模週期𝛬0−1=5.1𝜇𝑚。最後，計算並優化不同波導製程參數下模場疊加積分變化趨勢，預期在軟質子交換波導種產生高效率二倍頻轉換。

The development of laser optics promotes the realization of numerous nonlinear optics applications in research and practical purpose. For instance, integrated-blue light lasers can be applied in bio-medical, optical storage, laser printing, and high resolution photolithography.
Mg-doped Lithium Niobate (Mg:LN) possess high nonlinear coefficient, electro-optical coefficient, and low photorefractive damage effect, which benefit Mg:LN to be the candidate to generate blue-light laser source by nonlinear conversion. This thesis is for the purpose of optimizing the second harmonic generation (976nm to 488nm) conversion efficiency to approach theoretical efficiency in Soft Proton Exchange (SPE) Mg:LN waveguide. There are three factors contribute to the discrepancy between the empirical and theoretical conversion efficiency. First, high coupling loss result from the numerical aperture mismatch of fundamental mode (976nm) and waveguide. Second, imprecise design of QPM grating period from roughly estimated effective refractive index. Third, poor modes overlapping between fundamental and converted mode.
In the first part of this thesis, we utilize Mode field Diameter (MFD) method to measure the fundamental mode profile of SPE waveguide, and calculate the numerical aperture of our waveguide. Second, with the
effective refractive index measurement, we measured the effective refractive index with 976nm fundamental mode in SPE channel waveguide, calculate with the effective refractive index with 488nm fundamental mode and first order mode from prism coupler planer waveguide measurement result. We can get the real QPM period with SHG. Period 𝛬0−0=4.3𝜇𝜇 for 976nm fundamental mode generate to 488nm fundamental mode, and period 𝛬0−1=5.1𝜇𝜇 for fundamental mode generate to first order mode. Third, mode-overlapping integrals under different fabrication parameters are calculated and optimized for reducing the discrepancy between ideal and empirical conversion efficiency.

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