利用週期性極化反轉結構之光參數過程 產生可調可見光與寬頻光源

Abstract

首先在第一章、第二章的部分，簡單的介紹非線性頻率轉換、準相位匹配、隨機準相位匹配、光參振盪器的理論。第三章，主要是多段式晶體的設計與實驗細節介紹，在單一塊週期性鉭酸鋰晶體中，產生七道諧波，其中二、三、四、五道諧波為準相位匹配所產生的結果。由這些諧波所合成的脈衝會達到波包寬度為1.4 飛秒的轉換極限脈衝。

這些研究最終的目的是希望能夠透過光和物質的作用來控制物質裡的電子運動，為了要達到這個目的，我們需要發展能夠產生超寬頻頻譜和合成波型的技術。 第四章，主要是介紹寬廣可調的可見光，由近紅外光參振盪器產生近紅外光，近紅外光的非相位匹配二倍頻產生可見光波段，大約有百分之五的轉換效率，遠超過非相位匹配所產生的轉換效率。探討隨機準相位匹配的發現與模擬分析來解釋實驗的結果。最後是結論與未來展望，針對實驗上可以改進的地方與未來前景做探討。

This thesis includes three parts: In the first part, I will introduce the theory of quasi-phase match, random-quasi-phase-matching (RQPM) and optical parametric oscillation. In the second part, I will illustrate the design of cascade nonlinear crystal and the experiment results. Up to seven laser harmonics covering more than two octaves in frequency have been generated efficiently in a single PPLT crystal, permitting the syntehsis of 1.4 femtosecond pulses in a stable and compact setting.

Ultrashort subfemtosecond pulses with attosecond timing are essential for probing the evolution of electronic processes in atoms and molecules. The ultimate goal of these studies is to achieve coherent control of electronic motion in matter with light. To reach this goal, developing the ability to generate light pulses with an octave-spanning spectrum and having the ability to shape the pulses are required.

In chapter three, I will introduce the design of cascade nonlinear crystal and explain experiment results of generation of harmonic wave via cascade nonlinear crystal. Moreover, due to the inaccuracy from fabrication, in the chapter four, I will illustrate the theory and simulation and experimental results of random-quasi-phase-matching. We report broadly-tunable light generation by non-phase-matched intracavity SHG of a near-IR OPO with a several percent conversion efficiency. Simulation shows that random-phase-matching is the dominant cause of the efficiency enhancement. Finally, conclusion and future work will be included in chapter 5.