差分法求解时空分布的激光动力学模型

利用速率方程理论和差分法数值计算,建立了描述激光器内部粒子数密度和光子数密度的时间演化和空间分布的动力学模型.该方法完善了普通的激光速率方程理论,为了解激光能量的时间演化和空间分布提供了较好的理论模型. 关键词： 速率方程 差分法 动力学模型 铜激光     

自混频激光理论模型及应用

建立了在同一块非线性激光晶体上实现自混频激光的理论模型。该模型计入了具有任意腰斑大小的泵浦光和腔内基频光的空间分布,并将该模型应用到NYAB和Nd:GdCOB的自混频蓝光实验。理论分析预测和证实了一些实验结果,同时,讨论和总结了提高自混频激光输出效率的途径。     

Nd^3＋：YAG激光的光纤传输

首先叙述了光纤传输Nd^3 ：YAG激光的优点，接着分析了不同光纤和其传输Nd^3 ：YAG激光的特点。然后通过对光纤传输系统各部分的分析与设计，结合实际，设计了光纤耦合机构。最后，对来自于工件反射光问题提出了解决方案。     

新型Nd^3＋：Ca4GdO（BO3）3自倍频晶体Cr^4＋：YAG被动调Q激光特性研究

采用氙灯抽运自倍频晶体Nd^3 :Ga4GdO(BO3）3（简称Nd:GdCOB)，Cr^4 :YAG被动调Q，实现了Nd:GdCOB晶体被动调Q激光运转，测量了饱和吸收体Cr^4 :YAG不同小信号透过率小绿激光单脉冲的输出能量、脉冲宽度、重复率，给出了描述Nd:GdCOB晶体调Q工作原理的耦合波方程组，数值求解了该方程组，所得的理论结果与实验值相符合。     

激光局域网络的混沌控制及并行队列同步

本文提出并研究了"单队列-双参数"光电延时反馈控制条件下的激光局域网络的混沌控制及串联的动力学行为的并行队列"交叉驱动-反馈"网络同步实现,建立了该光学局域网络的数学物理控制模型.通过含时延超越方程理论的分析,预言了该光学局域网络是可以实现混沌控制的,且网络两路结点队列是可以实现实时引导控制到多个类周期状态上的,并通过并行队列同步方程理论证明并行串联队列同步是可以获得的.结果发现在可控的激光局域网络两个并行串联队列光路上,分别实现了网络队列结点的混沌控制并能够实现多个类周期的网络结点的并行串联队列同步,实现了络网结点激光器的2周期、3周期、4周期等状态的并行队列同步,以及其他多个类周期的队列并行同步和动态同步.还发现了两个类周期并行队列网络同步控制区域.本文还给出了激光局域网络"并行多点混沌载波同步发射及其在光学超宽带通信中应用"的一个案例并成功实现.这是一种新型的激光混沌局域网络控制系统,具有光局域网络光传送与光联接核心控制技术要素,具有复杂动力学系统与网络的多变量、多空间维度及并行两路不同队列混沌控制技术特点,还具有光网络超宽带通信功能等.其研究结果对局域网络、光网络的控制与同步、激光技术以及混沌的研究具有重要的参考价值.     

激光二极管抽运的全固体457 nm深蓝激光器

分析了Nd^3 :YVO4准三能级激光系统的实现方法，报道了用2W的808nm激光二极管抽运，实现了Nd^3 :YVO4的914nm激光振荡，并通过腔内倍频实现了457nm深蓝激光输出。蓝光最大输出功率为12mW，激光器阈值0 .9W，光－光转换效率为0.6%。     

4MV激光触发多级多通道开关特性

激光触发多级多通道开关是多路并联高功率脉冲装置的首选同步开关，对系统中各路脉冲功率系统的运行时序进行精确控制，以实现脉冲功率的有效叠加。由24个模块组成的10MAz—pinch实验装置（PTS）采用4MV激光触发多级多通道开关作为其系统中的主同步开关。该开关由～级激光触发间隙和21级自击穿间隙组成，采用匀场结构设计（即其所有间隙均为轴对称均匀场分布间隙），触发间隙电极设计为不锈钢Bruce电极；过压自击穿间隙电极设计为不锈钢冰壶型电极。采用场调整环强制调整开关区内的空间电场分布。     

紫外准分子激光损伤典型光学材料的特性分析

根据已经建立的紫外准分子激光损伤典型光学材料的理论模型,研究了准分子激光对透明光学材料（石英玻璃）和非透明光学材料（K9玻璃）的损伤特性,并结合实验结果证实了理论模型的有效性。研究表明：在准分子激光对非透明光学材料辐照下,激光光斑半径越大,产生的热应力和温度越小;脉宽越小,产生的热应力越大;随着脉冲数的增加,温度和热应力都逐渐增大。值得注意的是,当重频增加至45 Hz以上时,熔融损伤阈值开始低于应力损伤阈值,这说明当重频增加到一定程度时,非透明光学材料将首先产生熔融损伤,而不再是应力损伤。在准分子激光对透明光学材料辐照下,杂质微粒的半径和掩埋深度对光学材料温度场分布有着重要影响。但当杂质半径和掩埋深度超过一定的数值时,杂质粒子的存在与表面温度并无联系。理论模型能够较好地解释石英玻璃前/后表面相同的初始损伤形貌特征。     

低真空下紫外激光烧蚀铜诱导发光的机理

采用时间与空间分辨的光谱测量技术,测量了在低真空下XeCl紫外激光烧蚀金属Cu诱导产生等离子体发光羽的发射光谱随时间和空间的强度分布,利用快速同步照相的方法获得了发光羽的相片,结果发现发光羽的不同区域有不同的颜色特征。根据实验结果建立了非常可能的激光烧蚀诱导发光的理论模型,认为不同区域的主要发光机理不同,连续辐射背景光来自近靶处高能电子的运动而产生的轫致辐射;原子线的产生来自电子碰撞传能以及电子与离子的复合激发;离子线的产生来自电子与离子碰撞传能激发。此模型不仅能解释单一激发模型所能解释的实验现象,而且还能够很好地解释单一模型所不能解释的实验现象,低真空下紫外激光烧蚀铜诱导发光的机理与常压下相似,在此实验条件下可以更准确地揭示诱导发光的机理。     

激光二极管叠阵侧面泵浦多边形Nd∶YAG薄片激光器泵浦均匀性模拟仿真北大核心CSCD

阐述了一种激光二极管叠阵以zigzag方式侧面泵浦多边形Nd∶YAG薄片放大器的模拟研究,建模对Nd∶YAG晶体内泵浦光的吸收情况进行了深入的数值模拟与分析,研究了晶体的Nd^(3+)掺杂浓度对泵浦光分布均匀性的影响。研究表明,采用多个方向泵浦和zigzag泵浦方式易于实现介质内泵浦光的均匀分布,在晶体的Nd^(3+)离子掺杂浓度为0.25at.%时,仿真得到的泵浦光吸收分布为平顶型,分布的均匀性均为0.0505。对侧面泵浦多边形薄片激光放大器的进一步研究提供了参考。     

The effect of Fe doping in Potassium Hydrogen Phthalate single crystals on structural and optical properties

This work investigates the influence of iron doping on Potassium Hydrogen Phthalate (KHP) single crystals by the slow evaporation solution growth technique. Factors such as evaporation rate, solution pH, solute concentration, super saturation limit, etc. are very important in order to have optically transparent single crystals. As part of the work, the effects of metallic salt FeCl₃ in different concentrations were analyzed with pure KHP. Powder X-ray diffraction suggests that the grown crystals are crystallized in the orthorhombic structure. The functional groups and the effect of moisture on the doped crystals can be analyzed with the help of a FTIR spectrum. The pure and doped KHP single crystal shows good transparency in the entire visible region, which is suitable for optical device applications.The refractive indices along b axis of pure and doped KHP single crystals were analyzed by the prism coupling technique. The emission of green light with the use of a Nd:YAG laser (λ=1064 nm) confirmed the second harmonic generation properties of the grown crystals.     

Functional organic single crystals for solid‐state laser applications

Because of long‐range order and high chemical purity, organic crystals have exhibit unique properties and attracted a lot of interest for application in solid‐state lasers. As optical gain materials, they exhibit high stimulated emission cross section and broad tunable wavelength emission as similar to their amorphous counterpart; moreover, high purity and high order give them superior properties such as low scattering trap densities, high thermal stability, as well as highly polarized emission. As electronic materials, they are potentially able to support high current densities, thus making it possible to realize current driven lasers. This paper mainly describes recent research progress in organic semiconductor laser crystals. The building molecules, crystal growth methods, as well as their stimulated emission characteristics related with crystal structures are introduced; in addition, the current state‐of‐the‐art in the field of crystal laser devices is reviewed. Furthermore, recent advances of crystal lasers at the nanoscale and single crystal light‐emitting transistors (LETs) are presented. Finally, an outlook and personal view is provided on the further developments of laser crystals and their applications.     

一种掺钕光纤激光器与倍频技术实现的数值模拟

从双包层光纤激光器的速率方程和光传输方程出发，建立数学模型，进行数值计算并对掺钕光纤激光器输出功率沿光纤的分布以及不同光纤长度下抽运功率和输出功率沿光纤的分布进行了数值模拟。以808nm半导体激光器为抽运源，掺钕双包层光纤为增益介质，并以KTP作为倍频晶体，计算并模拟其倍频效率和相位匹配角。最后，对光纤激光器及其倍频的实现进行了模拟研究。结果表明，该光纤激光器能够高效率地实现可见光输出。     

激光自倍频晶体研究和应用进展

激光自倍频晶体是一类同时具有激光和非线性效应的复合功能晶体。以激光自倍频晶体制作的全固态激光器具有体积小,调整方便,稳定性高等优点。自1970年代以来,以LiNbO3,YAl3(BO3)4倍频晶体为基质的激光自倍频晶体实现了自倍频激光运转。近年来,以RECa4O(BO3)3(RECOB)为基质的激光自倍频晶体受到重视和广泛研究。本文从对激光晶体、非线性光学晶体及激光自倍频晶体的基本要求出发,在综述激光自倍频晶体研究历史的基础上,讨论了激光自倍频晶体中的基波和倍频光,探讨了NYAB和Nd:GdCOB一类晶体中晶体长度,Nd3+浓度和效率之间的关系。理论估算表明,当浓度适当,晶体长度10mm时,这两类晶体的光–光转换效率可达30%以上。本文总结了NYAB系列晶体的研究历程及RECOB系列激光自倍频研究的思路及取得的成果。在最近10年中,利用山东大学生长的Yb:YAB晶体,获得1.1 W自倍频绿光,光光转换效率为10%;在RECOB体系中,比较了各种晶体的特点,选定Nd:GdCOB为主要研究对象,经过晶体掺钕浓度和长度关系,位相匹配方向、膜系及热工程等多方面研究,获得了1.36 W的545 nm绿光输出,光–光转换效率为17.1%;输出功率为1.03 W时,半小时功率波动不超过1%。这是目前为止,Nd3+离子激光自倍频晶体的最好结果。文章最后介绍了激光自倍频晶体的可能应用。通过理论和实验分析,认为到目前为止Nd:GdCOB是以Nd3+为激活离子最后的激光自倍频晶体,而在Yb3+为激活离子时,Yb:YAB晶体最佳。     

四硼酸铝钕晶体及其小型全固态激光器

当前,全固态激光器在向万瓦级大功率方向发展的同时,也在向微型化发展。利用碟片全固态激光器可获得千瓦级以上激光,利用微片全固态激光器则可实现小体积、高密度、中小功率激光输出。获得高功率高密度激光的关键在于激光材料。本文从碟片和微片激光器的发展和对激光基质材料的要求出发,概述自激活激光晶体的研究,特别对四硼酸铝钕[NdAl3(BO3)4,简称NAB]晶体的结构、生长、性质及其作为有应用前景的小型片状激光器的候选材料作了详细的介绍。近期,采用面积为4×4 mm2,厚度为0.39 mm的微片NAB晶体,用885 nm半导体激光器为光源泵浦,获得了4.6 W的1.063 μm激光的有效输出,其斜效率达到64%,充分显示了NAB晶体作为自激活激光晶体在微片激光器中的应用前景。     

Self-focusing effects in a nematic liquid crystal at 10.6 $\mathsf{\mu}$m

E7 is a room temperature nematic liquid crystal that presents both a high temperature nematic-to-isotropic transition and a high positive dielectric anisotropy. The optical characteristics of this liquid crystal have been widely investigated in the visible region of the spectrum, while less experiments have been performed in the middle infrared spectral region, where, nevertheless, potential applications are important. We investigate the self-focusing of a middle infrared laser beam when it passes through a film of E7. We also take into account the heating of the liquid crystal film caused by the partial absorption of the laser light by means of a thermographic technique. A theoretical interpretation of the self-focusing phenomenon is given in terms of the reorientation of the molecules with respect to their unperturbed direction and an estimation of the average value of the elastic constants of the liquid crystal is given by fitting the experimental data with the theoretical model.Received: 16 April 2003PACS: 42.70.Df Liquid crystals - 42.65.-k Nonlinear optics - 42.55.Lt Gas lasers including excimer and metal-vapor lasers     

覆盖可见光波长的掺Er光纤飞秒光学频率梳

飞秒光学频率梳波长覆盖范围向可见光波长扩展对于碘稳频激光的绝对频率测量以及光钟研究中钟激光的绝对频率测量都具有十分重要的意义. 本文在自行研制掺Er光纤飞秒光学频率梳的基础上, 采用放大-倍频-扩谱的方案, 实现了激光输出波长向可见光波长的扩展. 掺Er光纤飞秒光学频率梳输出的一部分光激光脉冲, 功率约为8 mW, 首先经掺Er光纤放大器将功率提高到531 mW, 此后利用MgO: PPLN晶体倍频, 倍频后激光的功率为170 mW, 倍频效率为32%, 脉冲宽度为85 fs. 倍频后的激光通过光子晶体光纤进行光谱展宽. 通过优化入射光偏振状态可以实现波长覆盖500-1000 nm, 输出功率为85 mW, 耦合效率为50%. 采用小型化碘稳频532 nm Nd: YAG激光器输出激光与光学频率梳光谱展宽后的激光进行拍频可以获得30 dB的拍频信号. 覆盖可见光波长的掺Er光纤飞秒光学频率梳为可见光范围内激光的绝对频率测量提供了技术手段.     

Influence of transition metal doping on tris(thiourea)zinc(II) sulphate crystals

Optical, thermal and dielectric properties of Ni(II)-doped tris(thiourea)zinc(II) sulphate single crystals grown by slow evaporation solution growth technique has been investigated. The lattice parameters of the as-grown crystals were obtained by single crystal X-ray diffraction analysis. The modes of vibrations of different functional groups present were identified by FT-IR studies. The surface morphological changes are observed in the doped specimen. The structure and the crystallinity of the material were confirmed by powder X-ray diffraction analysis. The UV–vis optical absorption spectrum shows the lower optical cut-off at ∼284 nm and the crystals are transparent in the entire visible region. The relative second harmonic generation efficiency measurements reveal the enhancement of efficiency by doping with small quantities of Ni(II).