中文摘要支撑 作文
基于激光二极管（Laser Diode）端面泵浦全固态激光器具有结构紧凑，输出稳定，寿命长，效率高，应用前景广阔等优点，因此倍受国内外激光界的高度关注。本论文以Yb3+:KGd(WO4)2（Yb:KGW）和Yb3+:KY(WO4)2 (Yb:KYW)晶体为研究对象，研究了基于边界热对流的Yb:KGW和Yb:KYW晶体的激光热效应以及连续激光输出特性。主要研究内容可概括为以下几个方面。 1.介绍了LD泵浦掺Yb3+激光晶体的主要特性、研究现状以及发展前景；阐述
安徽地方志了LD泵浦固体激光器中的晶体在抽运过程中产生的热效应；概述了本论文的主要研究内容。
2.分析了LD端面泵浦掺Yb3+钨酸盐晶体的激光热效应。基于Yb:KGW和
Yb:KYW晶体的热传导具有各向异性的特点，建立了晶体在热传导条件下的模型。对稳态条件下的LD端泵掺Yb3+晶体热传导偏微分方程进行了数值解析，详细阐述了晶体热焦距实验测量原理。
3.研究了基于边界热对流的LD端泵Yb:KGW晶体的热效应。基于对LD端泵
Yb:KGW晶体工作特点的分析，建立了在热传导条件下的晶体模型。考虑晶体边界的热对流，借助有限差分法，运用FORTRAN语言进行编程，通过MATLAB软件调入FORTRAN程序，求解稳态各向异性介质热传导方程，第一次较精确地得到了晶体的温度场分布、端面热形变分布以及不同泵浦功率下的热焦距。研究结果表明，在泵浦吸收功率为14 W时，泵浦面最高温度达272.8℃﹑最大形变为0.48 μm，热焦距为4.8 cm。另外，进一步研究了LD 端泵Yb:KGW晶体的连续激光输出特性。
4.探究了考虑边界热对流的LD端面泵浦Yb:KYW 晶体的热效应。在对LD端
泵Yb:KYW激光晶体工作特点分析的基础上，建立了在热传导条件下的晶体模型。考虑晶体边界的热对流，运用FORTRAN语言通过有限差分法进行编程求解稳态各向异性介质热传导方程，首次较精确地得到了该晶体的温度场分布、端面热形变分布和不同泵浦功率下的热焦距。研究结果表明：在泵浦吸收功率为14 W时，泵浦面最高温度达243.8℃﹑最大形变为0.28 μm，沿I
x, z轴方向的热焦距分别为- 4.9 cm, 5.4 cm。另外，进一步研究了LD端泵Yb:KYW晶体的连续输出特性。杨诗丽
关键词：固体激光器；Yb:KYW 晶体；Yb:KGW晶体；有限差分法；热透镜效应陕西理工大学魏乐
甲氨基阿维菌素
分类号：TN248.1
蝗虫养殖前景
II
Thermal effects investigation on LD end-pumped Yb3+-doped
Potassium-Gadolinium Tungstate crystal
Abstract
Thanks to the unique advantages of diode-pumped all solid-state lasers, such as high efficiency, compactness, high stability and long lifetime, it has attracted more and more attention in the realm of lasers. In this paper, the thermal lensing study based on the heat transfer of diode-pumped Yb3+:KGd(WO4)2（Yb:KGW）and Yb3+:KY(WO4)2 (Yb:KYW) laser crystal was presented.Moreover, t he continuous-wave output characteristics of diode-pumped Yb:KGW and Yb:KYW was also demonstrated here.
1.The main properties, advantages, applications and developments of Yb3+- doped
Potassium - Gadolinium Tungstate laser crystal s were introduced briefly. The background and significance of the research on thermal effects of diode-pumped solid-state lasers were mentioned. The main content of the paper was presented briefly as well.
2.The theoretical analysis of the thermal lensing investigation based on the heat
transfer of diode-pumped Yb:KGW and Yb:KYW was presented. The model of Yb:KGW and Yb:KYW crystal under the heat transfer was established based on the characteristic of end-pumped anisotropic laser crystal. Numerical analysis on steady-state thermal conduct equation of LD end-pumped laser crystal considering the heat transfer was also presented in the paper. Moreover, the experimental measurement principle of thermal lens focal lens was also introduced.
3.Thermal lensing effects of diode-pumped Yb:KGW based on the heat transfer was
presented. Based on the features of LD end-pumped Yb:KGW laser crystal, the model was established. Considering the convective heat transfer on the side faces, the temperature distribution, pumped-face distortion and thermal focal length under different pump power were obtained by solving anisotropy heat conductive equation through finite difference method. Under the absorbed pump power of 14 W, the highest temperature located at the center of the pumped face was 272.8 ℃﹑the highest distortion was0.48 μm, and the thermal lens focal length was 4.8 cm.Moreover,t he continuous-wave output characteristics of diode-pumped
III
Yb:KGW was also demonstrated here.
4.Thermal lensing effects investigation of diode-pumped Yb:KYW based on the
heat transfer was also presented here. Based on the features of LD end-pumped Yb:KYW, the model was established. Considering the convective heat transfer on the side faces, the temperature distribution, pumped-face distortion and thermal focal length under different pump power were obtained by solving anisotropy heat conductive equation through finite difference method. Under the absorbed pump power of 14 W, the highest temperature located at the center of the pumped face was 243.8 ℃﹑the highest distortion was 0.28 μm, and the thermal lens focal length along x and z axis were - 4.9 cm and 5.4 cm, respectively. Moreover, t he continuos-wave output characteristics of diode-pumped Yb:KYW was also demonstrated here.
Key words:Solid-state lasers; Yb:KYW crystal; Yb:KYW crystal;Finite difference Method; Thermal lensing effect
CLC Number: TN248.1
IV
第一章导论
§1.1 掺镱激光晶体
近年来, 基于高输出功率、高发光亮度InGaAs半导体激光二极管的迅速发展以及掺镱离子激光材料在军事、通讯、医疗等方面的应用，适用于产生超短激光脉冲的掺Yb3+激光晶体因而倍受众多研究者的关注。 相比于掺Nd3+激光晶体，掺Yb3+激光晶体具有许多优良特性。第一，因为Yb3+离子的荧光光谱较宽，所以利用它可以实现飞秒激光器激光和可调谐激光器激光的有效运转。第二，由于镱离子的吸收谱在900 n m ～1100 nm之间, 所以它可以与InGaAs泵浦源进行有效的耦合。另外，由于镱离子的吸收线较宽，所以不需要严格的温度控制就可以获得相匹配的泵浦源泵浦波长（980nm）的激发。第三，因为掺镱离子激光晶体的荧光寿命可达1ms ～ 2 ms[1], 所以采用掺Yb3+激光晶体有利于超短激光脉冲和调Q激光脉冲的产生。第四，一般地讲，掺钕离子激光晶体的量子效率可达60 % ～70 %，而掺镱离子激光晶体的量子效率可以高达90 %以上，所以，掺镱离子激光晶体的量子效率相对较高。第五，因为掺镱离子激光晶体可以实现高浓度掺杂，所以可以通过这一途径来提高激光晶体单位长度的激光效率。最后，基于掺镱离子的激光晶体只有两个电子能级结构，基态2F7/2和激发态2F5/2, 所以, 从理论上讲，采用掺镱离子激光晶体可以避免浓度猝灭，粒子上转换和激发态吸收效应。
然而, 掺镱离子激光晶体还存在其它方面的一些不足。第一, 由于掺镱离子激光晶体的发射波段和吸收波段之间相距很近，所以这就需要对激光器所用的镜片进行比较精细的镀膜，这就相应地加大了晶体的制作难度，同时增加了激光器的生产成本。第二，掺镱离子的激光晶体具有准三能级激光运转机制，其吸收谱和发射谱有一定程度的交叠，这导致了激光晶体对激光波长的再吸收现象，从而加大了泵浦阈值功率。
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