準相位匹配鉭酸鋰寬頻藍光雷射晶片之研製

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-倍頻藍光雷射晶片之研製，以及光參-倍頻藍光雷射晶片之光學量測與特性分析。 理論部分，介紹非線性頻率轉換與準相位匹配理論，最後導出光參振盪器以及倍頻轉換理論。配合理論計算出鉭酸鋰晶體於不同操作條件下，滿足準相位匹配所需之週期大小。利用本實驗室發展的鎳金屬內擴散配合高壓電致極化反轉製成技術，應用於厚度0.5mm及0.75mm之共融鉭酸鋰基片製作，實驗中設計了光參-啁啾倍頻藍光雷射晶片，週期個別為7.76um與4.96um、4.98um、5um，成功研製出長16mm的高效率寬頻雷光雷射晶片。 光學量測部分，利用奈秒(~5ns)532nm綠光雷射做為泵浦源，設計一共振腔可共振930nm將所研製完成之雷射晶片置入，測量此光參振盪器之出光轉換效率。我們成功以350mW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，實現頻寬約0.8nm，斜線效率16%之465nm藍光。

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 cascade OPO-SHG 465nm blue laser chip, (3)the measurement and analysis of OPO-SHG blue light generators. First of all, I will introduce the mechanism of nonlinear frequency conversion and QPM theory, and it’s application to the optical parametric and second harmonic generation. Using Sellmeier equation, I design the QPM period of periodically poled LiTaO3(PPLT) for the above application. By taking advantage of the nickel-diffusion assisted electric poling process, I fabricated 930nm OPO devices of 5um periodicity on 0.5mm- and 0.75mm-thick congruent LiTaO3 substratee. Using this method, cascaded OPO-SHG PPLT device with a chirp structure in SHG segment, composed of 3 periods separate period of 4.96um, 4.98um, and 5um. With this design, the output of blue light contains high conversion effiency and broad spectrum. Using a 532nm, 5ns pulsewidth laser as the pump source, a 16mm long cascaded OPO-SHG chip in a concave laser cavity of 17mm length is shown to generate a 465nm blue laser. The spectrum is shown to have a 0.8nm bandwidth and an up-conversion effiency of 16% at 350mW green pump.