以鎂掺雜鈮酸鋰製作二倍頻藍光雷射波導元件之製程研究

Fabrication of second-harmonic-generation waveguide in MgO:PPLN for blue laser generation

余兆陞(Zhao-Sheng Yu)

指導教授 ： 陳彥宏

國立中央大學/理學院/光電科學研究所/碩士(2007年)

摘要

穩定、高效率的藍光雷射光源對於生物醫療、雷射列印、光學儲存與讀取以及量測系統是最主要的元件。在藍光半導體雷射尚未普及化，本研究選用5mol.%鎂摻雜鈮酸鋰，利用該材料本身的高非線性係數及高抗光折變損害等優良特性製作波長轉換元件，發展以准相位匹配(quasi-phase matching)技術及低損耗光學波導製作技術以期能有高效率的藍光雷射輸出。
本研究以退火式質子交換(annealing proton exchanged APE)波導的技術建立了寬度3.5μm、4μm、4.5μm以及5μm寬；深度4μm的APE波導模型，利用此波導模型我們可以模擬基頻光以及二倍頻光在波導中的等效折射率，經由準相位匹配(quasi-phase matched)的條件我們可以計算出二倍頻轉換過程所需的週期。利用此波導模型我們製作出低損耗的APE波導，其傳播損耗經量測得到α = 0.15 dB/cm。本研究中利用外加高壓電場法成功的在5mol.%鎂摻雜鈮酸鋰上製作出14.7μm以及14.8 μm兩種極化反轉的第三階週期性結構，經由本研究所歸納出的經驗公式可以有效地將晶格反轉面積與全部面積的比例(duty)控制在50%。

我們亦在軟質子交換波導(soft proton exchanged waveguides)及第一階的準相位匹配週期性反轉結構(?< 5 ?m)的製作上獲致初步的結果。本文提供製程的改進方案並正持續進行中。

關鍵字

鎂掺雜鈮酸鋰 ； 藍光雷射波導元件

並列摘要

A stable and efficient blue laser source has been one of the key elements used in biomedical, laser display, optical storage, and optical measurement systems. As an alternative to an attractive but not yet mature blue diode laser, in this work we try to develop a fabrication method of a quasi-phase-matching (QPM) second-harmonic generator in a low-loss optical-waveguide for achieving a high-efficiency blue laser based on a 5 mol. % MgO:LiNbO3 characterized by high optical nonlinearity and high optical damage resistance.
We have studied using a series of annealed proton exchanged (APE) channel waveguides of widths 3.5 μm, 4 μm, 4.5 μm, and 5 μm and a depth 4 μm to establish a fabrication model of a 976-nm frequency doubled MgO:PPLN APE waveguide. With this model, we can deduce the QPM grating period for this waveguided frequency doubling process via the calculation of the effective refractive indices of the fundamental and second-harmonic waves. We also fabricated a qualified low-loss APE waveguide with a measured waveguide loss of ~0.15 dB/cm. Besides, in this work we have successfully implemented a 3rd order QPM grating period of ~14.8 μm in a MgO:LiNbO3 crystal for the 976-nm waveguided frequency doubling process. We are possible to fabricate these MgO:PPLN with a QPM grating of 50% duty cycle.
We have also obtained some preliminary results on the study and fabrication of the soft proton exchanged (SPE) waveguides and 1st order QPM grating in a MgO:LiNbO3. We will discuss the improvement and practice schemes of these two advanced fabrication methods.

並列關鍵字

MgO:PPLN ； waveguide ； blue laser generation

參考文獻

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