準相位匹配鉭酸鋰白光雷射晶片之研製

Abstract

本篇論文主要由三大部分構成：準相位匹配與光參振盪器原理的介紹、光參振盪雷射晶片之研製，以及光參振盪紅、藍、白光雷射晶片之光學量測與特性分析。 理論部分，介紹非線性的頻率轉換作為引子，帶出本篇論文的中心理論”準相位匹配理論”，與其延伸出來的光參振盪理論，利用鉭酸鋰本身的色散性質配合理論計算，可以得到不同狀態下，準相位匹配週期性極化轉結構所需之週期大小。製程部分，利用本實驗發展的鎳金屬內擴散配合高電壓致極化反轉製程技術加以改良，應用於厚度0.5mm之共融鉭酸鋰晶片製作，實驗中設計了光參振盪紅光雷射晶片週期為11.6271um、光參振盪藍光雷射晶片週期為7.8963um與結合前述兩者的光參振盪白光雷射晶片，皆可以本技術成功研製。 光學量測的部分，利用奈秒(~20ns)532nm綠光雷射做為泵浦源，設計一共振腔可同時共振630nm、870nm之光參振盪系統，將所研製完成之雷射晶片分別置入，測量此光參振盪器之出光轉換效率。我們成功以450mW綠光泵浦單片準相位匹配級聯狀雷射晶片，以及雷射共焦腔之設計，實現630nm紅光19mW、435nm藍光27mW輸出，配合剩餘的532nm綠光30mW，可得76mW之白光輸出，光光轉換效率達到16.8% 。

This thesis is composed of three parts：(1) the theory of quasi-phase- matching(QPM) and the QPM optical parametric oscillator(OPO), (2) the fabrication technique of one-dimensional periodically poled congruent grown lithium tantalite(LiTaO3) for constructing a 532nm laser pumped optical parametric oscillator, (3) Demonstration of optical parametric red, blue, white light generators and the characteristics analysis of them. First of all, the mechanism of nonlinear optical generation will be introduced and then the theory of QPM and OPO will be explained. We applied the Sellmeier equation of LiTaO3 to design the QPM periods of PPLT for making the OPO chips. In the second part, the fabrication technique of PPCLT will be discussed. Furthermore, methods to improve the nickel-diffusion assisted electric poling process will be addressed. These technique allow the realization of domain period of 11.6um、7.9um respectively, for making optical parametric red blue light generators on PPLT of 20mm length, 0.5mm thickness. We finally applied two periodic domains in tandem in a single LiTaO3 crystal to facilitate cascaded QPM parametric process to current green input lasers to white light lasers. As an example, QPM-OPO chips that is able to current 532nm green input to generate singles waves 630nm、870nm simultaneously. By placing a 25mm-length PPLT chip inside a compact laser cavity of 30mm length, this compact design offers the generation of red light 19mW at 630nm, blue light 27mW at 435nm when pumped by a 20ns width green laser of 450mW. By doing so, an average output power of 76mW white light laser has been achieved under a 450mW input green pump, which corresponds to a conversion efficiency of 16.8 %.