準相位匹配寬頻白光雷射之研究

Study of Quasi-Phase-Matching Periodically Poled Lithium Tantalate for Broadband White Light Laser

侯濟民(Chi-Min Ho)

指導教授 ： 彭隆瀚

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.03289

摘要

本論文利用準相位匹配理論進行非線性光學中頻率轉換之研究，我們在0.75mm厚的鉭酸鋰(Lithium tantalite, LiTaO3, LT)基板，利用高電壓極化反轉的技術，製作出準相位匹配非線性轉換週期性極化反轉鉭酸鋰 (PPLT)非線性轉換光參晶體，置入光參振盪器中，產生高效率的藍光與白光雷射。
筆者利用級聯光參-多週期倍頻振盪結構，製作出波長可調式藍光晶體，再利用此結構使用變跡方法設計出寬頻高效率的藍光晶體，斜線效率約18%、頻寬1.83nm，且其波長頻寬變化平滑無明顯峰值之藍光465nm光源，這對於散斑的抑制有良好的效果。
接著本論文研究綠光光源的改良，筆者設計多週期變跡綠光倍頻結構，藉由寬頻寬的泵浦光源產生寬頻寬的綠光雷射。在實驗上，筆者成功製作出轉換效率約在10%，且波長頻寬大於5nm的綠光光源，此種綠光雷射光源將可降低散斑對比至5%左右。
最後利用藍光結構級聯光參紅光晶體，成功製作出寬頻高效率的白光光源，與先前相比，在使用新添購的NL204雷射且將光束光腰拓寬至300um(wo)後，在1W的泵浦綠光入射下，產生約200mW的白光輸出，其中藍光56mW、紅光83.03mW、綠光60.97mW，色度座標為(0.3141,0.3194,0.3665)、色溫為6489K、整體效率達20%，而藍光與紅光頻寬分別為1.2nm與1.12nm。

關鍵字

準相位 ； 白光 ； 雷射 ； 非線性 ； 跡變 ； 寬頻 ； 多週期

並列摘要

This thesis focuses on quasi-phase matching (QPM) frequency con-ver¬sion using periodically poled lithium tantalite (PPLT). It is composed of two parts： (1) Design and characterization of cascaded optical parametric oscillation (OPO) with second harmonic generation (SHG), and (2) the integration of optical structure of cascade OPO-SHG blue and OPO-red lasers to make blue light and white light laser.
First of all, multi-periodicity SHG cascading OPO is used to generate blue light laser with a wavelength of 465nm. Then with the help of apodizing, the phase delay can be reduced and thus the conversion efficiency and the generated blue linewidth can be improved to 18% and about 1.83nm, respectively.
Second, in order to improve green laser source with speckle reduction, multi-periodicity SHG with apodizing structure in green laser crystal is used. By using a broadband inferred pump made by an OPO process, the SHG green light conversion efficiency can reach about 10% and the linewidth of the green light can be expanded up to 5nm, which reduces the speckle contrast to less than 5%.
Finally, based on QPM PPLT, a 200mW white light laser source is fabricated when pumped by a 1W pulsed green laser. At an average green pump of 1W, 56mW and 83.03mW power for blue and red light were obtained. The total power is of 200mW white light with chromaticity coordinates (0.3141,0.3194,0.3665) and color temperature of 6489 K. The high conversion efficiency 20% was ascribed to the extended spectral line¬width of the blue and red bandwidth, exceeding 1nm.

並列關鍵字

QPM ； white light ； laser ； nonlinear optics ； apodization ； broadband ； multi-periodicity

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