多縱模近紅外光光學參量振盪器與可見光雷射之研究

Abstract

本論文主要研究鉭酸鋰和鈮酸鋰之頻率轉換於寬頻紅外光波段及寬頻綠光波段，利用高壓極化反轉技術，製作出需要的準項為匹配晶體，並將鉭酸鋰晶體置入共振腔中，成為可調波長之簡併泵浦光參振盪器，而利用光參振盪器產生之紅外經過鈮酸鋰晶體產生倍頻可見光。 本論文之簡併泵浦光參振盪器之紅外光可達200mW(泵浦光能量約為500mW)，而共振閾值約為54mW，斜線效率約為47%。當溫度超過簡併態溫度後，紅外出光能量隨溫度幾乎沒有大幅變動，頻譜隨著溫度提升而分成兩包，頻寬在接近簡併點時最寬。而由於架設之關係，我們成功在頻譜上看到comb shape的信號。 將光參振盪器產生之頻譜打入倍頻鈮酸鋰晶體後，我們得到一系列的可見光頻譜，而根據晶體設計不同產生之可見光頻譜相差甚大，但是基本上都可以跟原本泵浦的寬頻紅外光做關聯，因此我們可以從此關聯觀察到非線性轉換時的反應。

This thesis has basically two parts: (1) Build a degenerate pump optical parametric oscillator (OPO) with periodically poled lithium tantalate (PPLT) and two mirrors, and (2) using the source generated by OPO, we generate a series of signal in visible wavelength. First, in the degenerate pump OPO part, we have built a degenerate pump OPO with threshold about 54 mW and slope efficiency about 47%. We also observed comb shape signal in wavelength. And the span of com shape is about 1.5nm in wavelength domain and about 14 wavenumber (cm-1) or 450 GHz in frequency domain. We have generated a series of com shape signal in our IR spectrum by our OPO. Finally, we use comb shape IR as our next pumping source. We use two different PPLN as our experimental sample. For sample A, two different pumping source (the spectrum is different) but the result is very close, only a huge peak near 532 nm. For sample B, two different pumping source and result in two different spectrums in visible domain. The reason why two results are very different is that the range of the Quasi Phase Match period is different for each sample. We also observed comb shape signal in visible laser domain. And the span is also about 14 wavenumber (cm-1), this is because the comb shape signal in IR not only go SHG process but SFG process. Since the comb signal exist in both IR and visible domain, we can assign each other and to find the nonlinear process mechanism in the future.