【作者】 李光；

【导师】 王丽；

【作者基本信息】 北京工业大学 ， 光学， 2009， 硕士

【摘要】 课题来源于北京市自然科学基金项目(4062008)。论文对基于ZnGeP(2ZGP)晶体的中红外OPO-DFG系统所产生的可调谐输出特性进行了深入的理论分析。基于中红外激光晶体材料对激光进行频率变换产生的宽带可调谐中红外波段光源,在军事领域以及在环境监测、生物医药等民生领域中都有着广泛的应用前景。采用中红外激光晶体材料的光参量变频过程(如OPO、DFG)是获得宽带可调谐中红外光源的主要有效途径。因此,本课题的研究不仅具有一定的理论价值,而且也具有较强的实用意义。论文主要围绕着以下三个方面展开:1.阐述了课题研究的背景和意义。对中红外光源在军用民需领域的应用做了简单的介绍。介绍了目前常用的适合于中红外波段的非线性晶体材料。阐述了OPO技术的发展历史以及利用OPO和DFG技术获得中红外激光输出的研究状况。2.详细讨论了Yb:YAG激光晶体的能级结构和光学特性,通过建立准三能级调Q激光系统的理论模型,得到了调Q Yb:YAG全固态激光器的输出特性。利用MATLAB程序语言对其进行了数值模拟计算,并对其结果进行了分析。3.以三波耦合方程为出发点,介绍了角度相位匹配的基本原理以及正负单轴晶体的I、II类相位匹配。介绍了OPO和DFG运转的基本原理并对二者的异同进行了分析比较。基于中红外激光晶体材料的Sellmeier色散方程和角度相位匹配理论,对中红外激光晶体材料的光学特性以及DFG过程的调谐特性、允许参量及走离角度、线宽特性以及转换效率进行了理论上的分析。通过MATLAB数值模拟计算,获得了ZGP晶体的折射率色散曲线,以及其在DFG过程中的有效非线性系数、角度调谐、允许角以及走离角等理论曲线,并且与AgGaSe2(AGSe)和AgGaS2(AGS)晶体的相应曲线进行了比较;得到了ZGP晶体抽运光线宽对DFG输出光线宽影响以及抽运光强度、晶体长度、相位失配对转换效率影响的理论曲线,同时与另外两种晶体相应曲线进行了比较。经过对三种晶体进行比较分析,我们得出结论:在DFG产生可调中红外输出的特性上,ZGP和AGSe两种晶体要优于AGS;但在转换效率方面,ZGP晶体要远优于AGSe和AGS。这与国内外已报道的实验数据相吻合。证实了ZGP晶体是一种可以产生可调谐中红外输出的较为理想的非线性光学晶体。更多还原

【Abstract】 This thesis has focused on research of a mid-infrared laser using nonlinear optical crystal supported by Beijing Nature Foundation (No.4062008), the properties of tunable mid-infrared OPO-DFG system based on the crystal of ZnGeP2(ZGP).The tunable broadband of mid-infrared laser source was generated that the mid-infrared laser crystal has broad prospects for the applications in the realm of military, environmental monitoring and biological medicine, etc.. Optical parameter frequency conversion in mid-infrared laser crystal is an effective method to obtain a tunable broadband mid-infrared output. Therefore, this research has not only definite theoretical signification, but also strong practical function. There are three research work emphases in this paper as follows.1. The background and significance of research work have been explained. The application introduction of mid-infrared light source in military and livelihood fields, and the nonlinear optical crystal is very useful in the mid-infrared laser have been summarized. In addition, the developing history of OPO and DFG with nonlinear optical crystal to obtain mid-infrared laser output has been reviewed.2. The crystal energy structure and optical characteristics of Yb:YAG have been discussed in detail. The output characteristics of Yb:YAG all-solid-state laser have been obtained by establishing the theoretical model of Q-switched in quasi-three-level laser system. The output characteristics have been studied by simulating with MATLAB program.3. Based on resonant three wave coupling equations, The basic principle of angle tunable in phasemaching type-I, and -II for a positive uniaxial crystal and negative uniaxial crystal have been theoretical analyzed and simulated. In addition, the principles of OPO and DFG with nonlinear optical crystal have been analyzed and compared. The optical properties of mid-infrared laser crystals and the tuning characteristics, parametric optics linewidth , acceptance angle, walk-off angle, conversion efficiency in the process of ZGP-DFG have been analyzed based on sellmeier equations of mid-infrared laser crystals and the theory of angle-phase-maching. Through numerical simulation with MATLAB, the curves of refractive index dispersion of ZGP and the curves of effective nonlinear coefficient, angle tuning and acceptance angle, walk-off angle for ZGP-DFG have been obtained and compared with relative crystal of AgGaSe2 (AGSe) and AgGaS2 (AGS). In addition, the relation curves of pump linewidth will influence DFG output linwidth, and the pump intensity, crystal length, phase-mismatch will influence the output conversion efficiency have been obtained, and compared with of AGSe and AGS. By making comparison of the three crystals, the conclusion was that: the tunable mid-infrared output of DFG with ZGP and AGSe were superior to AGS; in obtaining high conversion efficiency, ZGP was far superior to AGSe and AGS, which have been consistent with the experimental results in domestic and overseas researcher’s. Therefore, ZGP has been approved to be an ideal nonlinear laser crystals for generating tunable mid-infrared coherent radiation.更多还原