【作者】 夏林中；

【导师】 阮双琛； 苏红；

【作者基本信息】 华中科技大学 ， 光学工程， 2009， 博士

【摘要】 光参量振荡器是产生宽带连续可调谐的中红外激光的一种非常重要的手段，它能够将一个泵浦激光转换为相干输出的信号光和闲频光，且可以在较宽的频率范围内实现连续可调谐输出。另外，光参量振荡器除了可以实现小型化与全固化外，还具备了转换效率高、结构简单、工作可靠度高等优点。近些年来，随着一批新的优质非线性光学晶体的发明，尤其是掺氧化镁的周期极化铌酸锂晶体（MgO：PPLN）的出现，以及非线性频率变换和宽带连续可调谐激光技术的迅速发展，使得光参量振荡器这一研究领域取得了很多重要的成果。这也使得光参量振荡器在很多领域得到了广泛的应用，如相干反斯托克斯拉曼散射（CARS）谱测量、激光光谱学研究、环境监测、遥感、材料处理、激光测距、红外干扰和对抗等。光参量振荡器及其应用技术研究的发展在现代科技发展中将起着越来越重要的作用，因此它的研究前景将十分看好。作者进行了基于PPLN晶体和MgO：PPLN晶体的准相位匹配（QPM）宽带连续可调谐的中红外光参量振荡器的理论与实验研究工作；同时也对光参量产生器作了相关的实验研究。主要工作如下：（1）对国内外有关宽带连续可调谐的中红外光参量振荡器的研究现状以及发展趋势做了广泛的调研工作，且以此明确了自己研究工作的重点和方向。（2）分析了与宽带连续可调谐中红外光参量振荡器相关的一些基础理论，具体如光参量振荡器和产生器中的三波互作用理论、准相位匹配理论、光参量振荡器的基本理论等。尤其对光参量振荡器的增益、阈值、转换效率等特性进行了系统地分析。并且简要介绍了如何设计基于PPLN晶体和MgO：PPLN晶体的光参量振荡器。（3）报道了宽带连续可调谐的中红外单谐振PPLN-OPO的研究工作。泵浦源为1.064μm声光调Q Nd：YAG全固态激光器，PPLN晶体的尺寸为50mm×10mm×0.5mm，极化周期分别为26.5μm、27.5μm、28.5μm、29.5μm和30.5μm，在40-200℃范围内调节PPLN晶体的温度和极化周期，获得了2.80-3.17μm、3.34-3.60μm、3.77-3.97μm、4.15-4.32μm和4.48-4.62μm的闲频光调谐输出，且在3.09μm处，获得了最大闲频光输出功率1.23W。（4）报道了宽带连续可调谐的中红外单谐振MgO：PPLN-OPO的研究工作。泵浦源为1.064μm声光调Q Nd：YAG全固态激光器，MgO：PPLN晶体的尺寸为50mm×10mm×1mm，极化周期分别为26.5μm、27.5μm、28.5μm、29.5μm、30.5μm和31.5μm，在50-200℃范围内调节MgO：PPLN晶体的温度和极化周期，获得了2.83-2.89μm、3.10-3.38μm、3.57-3.78μm、3.95-4.12μm、4.28-4.46μm和4.65-4.79μm的闲频光调谐输出，且在3.33μm处，获得了最大闲频光输出功率2.17W，较之PPLN-OPO的最大输出功率增加了许多。（5）首次报道了宽带连续可调谐的中红外单谐振双MgO：PPLN晶体串接的OPO的研究工作。泵浦源为1.064μm声光调Q Nd：YAG全固态激光器，两个MgO：PPLN晶体的尺寸均为40mm×10mm×2mm，极化周期分别为26μm、26.5μm、27μm、27.5μm、28μm、28.5μm、29μm、29.5μm、30μm、30.5μm和31μm，在40-200℃范围内调节两个MgO：PPLN晶体的温度和极化周期，获得了2.789-4.957μm的闲频光调谐输出，且在3.344μm处，获得了最大闲频光输出功率2.23W，较之MgO：PPLN-OPO的最大输出功率有所增加。（6）首次报道了1.342μm泵浦的宽带连续可调谐的中红外双MgO：PPLN晶体串接的OPG的研究工作。泵浦源为1.342μm高功率准连续声光调Q Nd：GdVO₄全固态激光器，两个MgO：PPLN晶体的尺寸均为40mm×10mm×2mm，极化周期分别为29μm、29.5μm、30μm、30.5μm、31μm和31.5μm，在40-200℃范围内调节两个MgO：PPLN晶体的温度和极化周期，获得了4.144-4.851μm的闲频光调谐输出，且在4.144μm处，获得了最大闲频光输出功率340mW。更多还原

【Abstract】 Optical parametric oscillator （OPO） is one of the most important ways to get widelycontinuous-tunable mid-infrared lasers. The pump light could be converted into signal lightand idler light by this way. Meanwhile, it can generate widely tunable coherent light.Furthermore, the OPO possess the characteristics of high efficiency, simple structure, andhigh work stabilization and it could be made in small and all-solid. In recent years, with theinvention of the new nonlinear crystals, especially the invention of the periodically poledMgO-doped lithium niobate （MgO:PPLN） crystal, and the rapid development of thenonlinear frequency transformation and the technologies for the tunable laser, lots ofimportant breakthroughs have been made in the field of OPO. The OPO has been used inmany fields, such as CARS, laser spectroscopy, environmental monitoring, remote sensing,material handling, laser ranging, infrared interference and countermeasure. Therefore, theresearch on the OPO and its applications will become more and more important for thedevelopment of the modern science and technology. The perspective of the studies on OPOis bright.The author has done some theoretical and experimental research work onquasi-phase-matched （QPM） widely continuous-tunable mid-infrared OPO which is basedon PPLN crystal and MgO:PPLN crystal. Meanwhile, some experimental research work onoptical parametric generator （OPG） has been done, too. The main research works aresummarized as follows:（1） The worldwide research status at present and the developing trend in the future ofthe widely continuous-tunable mid-infrared OPO have been studied and investigated.Therefore, the important points and the direction of our own research work are clear.（2） The interrelated basic theories of the widely continuous-tunable mid-infrared OPOhave been analyzed and discussed. Such as the three wave interaction in the OPO or OPG,QPM theory, and the basic theory of the OPO. Furthermore, the gain, threshold value, andconversion efficiency of the OPO have been analyzed. And introduced how to design theOPO system based on PPLN and MgO:PPLN. （3） The research work of the widely continuous-tunable mid-infrared single resonantPPLN-OPO has been reported. The pump source is an acousto-optically Q-switchedNd:YAG laser. The dimension of the PPLN crystal is 50mm×10mm×0.5mm and the gratingperiods of the PPLN crystal are 26.5μm, 27.5μm, 28.5μm, 29.5μm, and 30.5μm. The idleroutput ranges of 2.80-3.17μm, 3.34-3.60μm, 3.77-3.97μm, 4.15-4.32μm, and 4.48-4.62μmare obtained by changing the temperature of the crystal from 40 to 200℃and the gratingperiods of the PPLN crystal. And the obtained maximum idler output power is 1.23W at3.09μm.（4） The research work of the widely continuous-tunable mid-infrared single resonantMgO:PPLN-OPO has been reported. The pump source is an acousto-optically Q-switchedNd:YAG laser. The dimension of the MgO:PPLN crystal is 50mm×10mm×1mm and thegrating periods of the MgO:PPLN crystal are 26.5μm, 27.5μm, 28.5μm, 29.5μm, 30.5μm,and 31.5μm. The idler output ranges of 2.83-2.89μm, 3.10-3.38μm, 3.57-3.78pμm,3.95-4.12μm, 4.28-4.46μm, and 4.65-4.79μm are obtained by changing the temperature ofthe crystal from 50 to 200℃and the grating periods of the MgO:PPLN crystal. Theobtained maximum idler output power is 2.17W at 3.33μm. And the maximum idler outputpower of the MgO:PPLN-OPO is larger than that of the PPLN-OPO.（5） The research work of the widely continuous-tunable mid-infrared single resonanttwin-MgO:PPLN cascaded OPO has been reported firstly. The pump source is anacousto-optically Q-switched Nd:YAG laser. The dimension of the two MgO:PPLNcrystals is 40mm×10mm×2mm and the grating periods of the MgO:PPLN crystal are 26μm,26.5μm, 27μm, 27.5μm, 28μm, 28.5μm, 29μm, 29.5gm, 30μm, 30.5μm, and 31μm. Theidler output range of 2.789-4.957μm is obtained by changing the temperature of the crystalsfrom 40 to 200℃and the grating periods of the two MgO:PPLN crystals. The obtainedmaximum idler output power is 2.23W at 3.344pm. And the maximum idler output powerof the twin-MgO:PPLN cascaded OPO is larger than that of the MgO:PPLN-OPO.（6） The research work of the widely continuous-tunable mid-infrared twin-MgO:PPLNcascaded OPG which based on 1.342μm pump source has been reported firstly. The pumpsource is a diode-pumped Q-switched Nd:GdVO₄ laser operated at 1.342μm. Thedimension of the two MgO:PPLN crystals is 40mm×10mm×2mm and the grating periods of the MgO:PPLN crystal are 29μm, 29.5μm, 30μm, 30.5μm,31μm, and 31.5μm. The idleroutput range of 4.144-4.851μm is obtained by changing the temperature of the crystalsfrom 40 to 200℃and the grating periods of the two MgO:PPLN crystals. The obtainedmaximum idler output power is 340m W at 4.144gm.更多还原