週期性極化反轉製程研究及堆疊PPLN產生高能量紅外光雷射

Study of Periodic-poling Techniques and use staked PPLNs for high-energy infra red laser generation

梁鈞強(Chun-Chiang Liang)

指導教授 ： 楊士禮

國立清華大學/電機資訊學院/光電工程研究所/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00781

摘要

利用加高電壓方式製作出的週期性極化反轉晶體，其準相位匹配(quasi-phase matching)技術拓展了非線性晶體的應用範圍且提升了非線性光學轉換效率。而QPM-OPG所產生的近、中紅外光波段的光源，在軍事、生物醫療、環境監測、遠距離量測等皆有廣泛的應用。
本論文致力於週期性極化反轉鉭酸鋰和鈮酸鋰晶體。為了產生高能量紅外光波長，我們選擇非線性係數較大的鈮酸鋰晶體，且嘗試製作1mm厚的PPLN晶體。利用外接電阻降低極化反轉電流的方式，且採用兩階段極化反轉方法，成功克服了1mm厚晶體在高電壓下易破裂的問題，並製作出長度為40mm、寬5mm、厚1mm之週期性極化反轉鈮酸鋰晶體。因受限於單塊晶體光損害閥值太低(約2.3J/cm2)，無法打入高能量入射光源以產生更高的紅外光能量。我們利用多片相同的週期性極化反轉晶體堆疊且搭配微透境陣列做組合，利用微透境陣列中各單體透鏡分散入射光能量，利用陣列式光源打入堆疊的晶體中，以得到更高能量的紅外光光源。在光參數產生器結構中，打入12mJ入射光可產生2.8mJ signal光源，其產生效率約為23%。若考慮晶體的端面反射和反射鏡的損耗，訊號光轉換效率約有30%以上。

關鍵字

週期性極化反轉 ； 光參量產生

並列摘要

Using high voltage could make a periodically poled crystal, and the QPM(quasi-phase matching) technique not only expands the applications in many domains but also enlarges the conversion efficiency of the non-linear optics. The infra red which produced by the QPM-OPG could apply to the military, medical treatment, environmental monitor and long distance measurements…etc.

The dissertation was devoted to fabricating periodically poled Lithium Tantalite(PPLT) and Lithium Niobate crystal. For producing high energy infra red, we choose the Lithium Niobate which has more great non-linear optical coefficient and we try to fabricate 1mm thickness PPLN. Connecting a resistance to limit the poling current, and we utilized two stages methods to fabricate PPLN crystal. Not only one overcame the problems during high voltage poling (~22kV) and collected many valuable parameters. We had succeeded in fabricating 40mm-long, 5mm width and 1mm thickness PPLN with period 29.6 um. Owing to the damage threshold of single PPLN crystal is too low to pump more energy, we try to combine staked PPLNs with micro-lens array to produce more energy of the infra red. The large energy pumping will be separated into many individual pieces by micro-lens array and incidents in the different location of cross section on PPLN. In OPG experiment, at 12 mJ pump pulse energy, it generated 2.8mJ pulse energy of the signal. Considering no AR coating and the loss of the reflector, the total conversion efficiency is about 30%.

並列關鍵字

PPLN ； OPG

參考文獻

[24] 蔡立酋,“週期性極化反轉製程研究以及利用單一週期鉭酸鋰晶體產生紅光和藍光雷射,”國立清華大學光電所碩士論文(2008).

[1] Koichiro Nakamura,Jonathan Kurz,Krishnan Parameswaran

and M.M.Fejer“ Periodic poling of magnesium oxide doped

lithium niobate,＂J.Appl.Phys.91,4528.

LiTaO3 for Bulk Quasi-Phase-Matched Devices,＂Ferroelectrics