奈秒級光學參量振盪器應用於白光雷射產生器之研究

Abstract

本論利用準相位匹配理論進行非線性光學中頻率轉換之研究，我們在0.75mm厚的鉭酸鋰(Lithium tantalite, LiTaO3, LT)基板，利用高電壓極化反轉的技術，製作出準相位匹配非線性轉換週期性極化反轉鉭酸鋰 (PPLT)非線性轉換光參晶體，置入光參振盪器中，產生高效綠的白光雷射，筆者先對共振腔模態進行優化，再來分別先對藍光與紅光結構進行量測。 筆者以532nm作為綠光泵浦源採用級聯光參-倍頻架構。，首先利用光參結構產生930nm的紅外光後，利用其波長可調頻寬增益的特性，將它級聯多週期倍頻結構後，換成465nm的藍光晶體，製作出一波長頻寬為1.38nm斜線效率達20%的寬頻藍光晶體。紅光部分使用光參結構，轉換出630nm的紅光，經過量測後，製作出一斜線效率為50%的高效率紅光晶體。 利用上述的經驗，將紅藍光製作在同一基板上，于500mW泵浦綠光入射下，藍光輸出約41.69mW、紅光為59.69mW，總共可產生生約150mW的白光，其色度座標為(0.313,0.334,0.353)、色溫為6332K、整體效率達30%，而藍光與紅光的波長頻寬分別為1.38nm與1.91nm，可以大幅抑制雷射投影所面臨的光斑現象

This thesis is focused on quasi-phase matching (QPM) frequency conver¬sion using periodically poled lithium tantalite (PPLT). It is com-posed of two parts： (1) Design and characterization of cascaded optical parametric oscillation (OPO) with second harmonic generation (SHG), and (2) the integration of optical structure of cascade OPO-SHG blue and OPO-red lasers to make white light lasers. For the design of laser cavity, I worked out the issues of cavity mode matching and laser beam quality, laser beam quality and choose the proper beam size to characterize the nonlinear optical process. Second, I use single pass gain (parametric gain) to simulate the band¬width of OPO, then cascading the SHG part. By this simulation, I can pre¬dict the bandwidth of blue light, and then used the mechanism of single pass parametric gain to calculate the spectral bandwidth of QPM OPO. The letter allows us to predict the spectral acceptance of SHG where cascaded with an OPO segment. We demonstrate a broadband (~1.38nm) 465nm blue laser with 20% conversion efficiency when the device is composed of 10mm long OPO and 3mm long SHG segment. Finally, I fabricate 150mW white light laser source based on an QPM PPLT when pumped by a 500mW pulsed green laser. At average 500mW of green pump, we obtained 41.69mW and 51.69mW power for blue and red light. It amounts to a generation of 150mW white light with chromaticity coordinates (0.313, 0.3342, 0.3528) and color temperature of 6332