鎳擴散非線性光子晶體波導之寬頻綠光雷射技術研究

Abstract

本論文主要研究利用薄平面鏡作為Fabry Perot濾光鏡，使其作為光參振盪器的輸出鏡以產生梳狀的寬頻紅外光譜。其頻譜間峰值距約為約為14.3cm-1，與Fabry Perot濾光鏡厚度模擬結果之自由光譜區14.4cm-1非常接近。利用光參振盪器產生的梳狀寬頻紅外光作為基頻光通過多週期反轉鈮酸鋰以產生綠光雷射，同樣產生梳狀寬頻綠光光譜，其峰值間距為16cm-1，與梳狀寬頻紅外光結果非常相似。另外我們比較了晶體兩方向入射的差別與不同週期涵蓋的差別。 與過去研究是先金屬擴散再極化反轉晶體不同，本論文則探討先極化反轉再進行金屬擴散。週期選定29.5um，區域反轉之晶體分別以700˚C與800˚C進行鎳擴散以製作平面波導。利用兩相互垂直的偏振片作為顯微鏡系統對鎳擴散深度的觀察，結果在700˚C 擴散深度約為6um。而800˚C擴散深度約為27um。並且發現在800˚C擴散雖然週期之深度較深，但有反轉結構合併的現象，使得頻譜變窄。

In this thesis, based on Fabry Perot effect, a thin flat is used as the output mirror for the optical parameter oscillator(OPO) ,to fabricate a broadband comb Infrared source。The peak spacing of these comb signals is about 14.3cm-1,which is it very close to the simulated free spacing range of a Fabry Perot etalon 14.4cm-1 . IR combs are then used as fundamental frequencies of the multi-period periodically-poled lithium niobate (PPLN)device for generate of broadband combs green laser。The peak spacing of broadband combs green laser is about 16 cm-1, which is very close to that of the comb IR source. For comparison, pumping from two different directions and periods of different ranges are studied. Moreover, the process of first poling and then Ni diffusion is used for the fabrication of waveguides, which is different from the conventional process that uses Ni diffusion first and then poling. Ni planar waveguides are diffused on PPLN substrates of the same period 29.5 um but at 700˚C and 800˚C. Diffusion depths measured by using microscope system with two crossed linear polarizers are 6 um and 27 um for diffusion at 700˚C and 800˚C, respectively. The periods of the PPLN substrates diffused at 800˚C are deeper but merged, and therefore the resulting frequency bands are narrowed.