2μm波段激光晶体研究进展

综述了以Ho、Tm、Er为激活离子、以YAG、YAP及YLF为基质的2μm波段激光晶体的特点及应用背景,详细讨论了几种重要2μm波段激光晶体的能级结构、光谱特性及器件研究进展,指出了适合LD泵浦是今后2μm波段激光晶体的发展方向.     

激光晶体YAG中E_r~（3＋）离子最佳掺杂浓度

测试了２ａｔ．％Ｅｒ：ＹＡＧ晶体的吸收谱，荧光谱，４Ｉ１１／２、４Ｉ１３／２态荧光衰减曲线．由荧光衰减曲线拟合得到荧光寿命τ０和描述离子间的相互作用微参量ＣＤＡ，并将其代入作者推导得到的最佳掺杂浓度的近似式，计算出Ｅｒ３＋离子在ＹＡＧ晶体中的最佳掺杂浓度，并与实验结果进行了比较     

Cr,Yb:YAG晶体的光谱性质

采用提拉法生长了原子分数为10％的Yb和不同掺杂浓度Cr的Cr,Yb:YAG激光晶体.测试了室温下晶体的吸收光谱、荧光光谱和荧光寿命.随着晶体中Cr离子掺杂浓度的增加,晶体在1.03μm处的吸收系数增大、荧光强度和荧光寿命下降,同时Yb³⁺→Cr⁴⁺能量转移效率增加、量子效率降低.确定了Cr,Yb:YAG晶体中Cr的最佳浓度值.     

固体激光器单晶

1.前言自从约10年前第一次在光学领域用红宝石晶体通过感应辐射产生振荡现象的报告发表以来,利用含有激活离子的固体结晶,在红外光和可见光波段实现了多种激光器。与气体激光器相比,固体激光器的特点是激活离子的密度大,因而单位长度的平均增益和输出功率大,适于装置的小型化;振荡频带宽,适于发生宽度窄的光脉冲。固体激光器的研究有二股潮流。一股就是设法实现峰值功率大的激光。在这方面,把能量充分蓄积在激活离子中使共振腔的Q     

LD端面抽运长方形激光晶体的热效应

通过对二极管激光器端面抽运激光晶体工作特点的分析,提出了长方形激光晶体热模型。在热模型中考虑了激光晶体具有沿轴向对称加热、周边恒温等特点。利用热传导方程得出了激光晶体内部温度场和端面热形变场的一般解析表达式。研究结果表明,若使用输出功率为18W的二极管激光器端面抽运Nd:YVO4晶体(钕离子掺杂质量分数为0.5%),抽运光斑为0.4mm时,长方形激光晶体抽运端面具有267.6℃的最大温升和发生6.2μm的最大热形变量。对激光晶体产生的温度场和端面热形变场的研究为解决晶体热透镜效应、提高激光器的性能起指导作用。     

掺镨硼酸钙氧钆(GdCOB:Pr)晶体的光谱性能

首次生长了新型激光晶体GdCa4O(BO3)3:Pr简称（GdCOB:Pr),测量了它的室温透过谱,并在530nm激光激发下测量了晶体的荧光发射,分析并标定了Pr^3 离子的能级跃迁对应的峰值。分析了掺杂稀土离子对晶体紫外吸收边的影响。     

低维纳米光子晶体的制备及在有机激光谐振腔的应用

采用电子束曝光技术以及反应离子刻蚀技术,提出一种简单可控、低成本制备有序排布的一维和二维光子晶体阵列的方法。通过有效的控制刻蚀工艺参数,实现对光子晶体在尺寸、周期和表面结构等进行精确控制目的。此外,以一维光子晶体为衬底,利用甩膜方法成功地制得分布反馈式高分子有机激光器。光泵结果表明,该激光染料的放大自发辐射的阈值为260kW/cm2、半波宽为0.22nm。     

晶体生长技术的改进

激光棒是固体激光器最重要的元件,大多采用单晶棒作为激活增益介质。目前已能生长多种激光晶体,但成功率却各不一样。最成功的一些晶体要算通用的石榴石晶体族,其中又以钇铝石榴石(YAG)为广泛利用的激光材料。因此,改善Nd:YAG激光器     

祖母绿激光晶体的水热法生长

祖母绿是一种优秀的宽带可调谐激光晶体材料,本文使用温差水热法和特殊的培养料分离技术,通过控制籽晶切向和石英-籽晶相互层叠式布置实现了一个高压釜单个生长周期多个单晶体的缓慢生长,晶体形状为厚板状和短柱状,通过吸收谱、显微镜观察、激光对晶体中散射颗粒检测和初步的激光实验认为,本期合成的祖母绿晶体质量优异,晶体特征和世界其他国家合成的晶体一致.     

氟化物激光晶体及其在固体激光器中的应用

固体激光基质材料可以分为晶体、玻璃、光纤和陶瓷。相对于其他材料,晶体的优点表现在热导率高、荧光谱线窄、硬度比较大等方面,因而在固体激光器中获得了更广泛的利用。作为一类重要的激光基质材料,氟化物激光晶体种类多,研究活跃,一直是激光材料的热点之一。介绍CaF_2、LaF_3、MnF_2、ZnF_2、KMgF_3等激光晶体基质以及Nd、Er、Cr、Yb、Co等离子掺杂激光晶体,特别是MgF_2、YLF、LiSAF等激光晶体,探讨了这些材料的发光特性,并与YAG等常用氧化物激光晶体进行了比较。与其他激光介质相比,氟化物激光晶体具有自发荧光寿命长、折射率受温度影响小、热透镜效应小、热稳定性好等优点,决定了其在固体激光器领域特殊的应用价值。在对氟化物晶体的激光器应用分析基础上,展望了氟化物激光晶体未来的研究前景。     

多基地声纳系统检测性能分析

分析了多基地声纳系统的检测性能。利用检测统计量,推导了在背景噪声为高斯白噪声、信号为高斯随机过程的情况下,主动多基地声纳系统的最优检测接收机。指出主动多基地声纳系统的最优检测接收机为匹配滤波器。然后,提出了一种基于＂和检测＂原理的简化检测接收机,并分析了它的检测性能及基地选择原则。结果表明：对于这种简化的检测接收机,当一个基地的检测性能远远优于其它基地时,如果再将其它基地融入到处理系统中,系统的检测性能不会得到明显提高,甚至可能会下降;另一方面,当各个基地的输入信噪比接近时,参与检测的基地个数越多,系统的检测性能越好。     

飞秒激光空间选择性诱导玻璃微结构及应用

利用飞秒激光与玻璃的非线性相互作用，可以对玻璃进行空间选择性微观改性与修饰，赋予新的光功能．本文介绍飞秒激光的持点及其对玻璃微结构的改性，以及近年来利用飞秒激光进行玻璃的缺陷控制、光活性离子(稀土、过渡和重金属离子)价态操作、微晶析出与折射率调控及其在光开关、波分复用、波导型有源器件、光子晶体等微光学器件的制备及光学集成领域应用的进展．     

Ionization dynamics in the laser plasma in a low pressure gas target

In Xe-laser-plasma short-wave-radiation sources, the laser-energy-to-EUV conversion efficiency (CE) turns out to be substantially lower than theoretical expectations. An estimation made in the present work is evidence of what a long period of the primary ionization, lasting up to a moment when high-Z ions appear to emit short-wave photons, can be considered as a main cause for the low CE values. During that period the plasma remains low-ionized and absorbs weakly the laser energy. Data deduced from laser light absorption measurements confirm the estimation above. A preionization of the gas target with the UV excimer laser pulse is proposed as a method to accelerate the ionization process.     

Divergence temporal dynamics of a Q-switched laser

I address the influence of the direct coupling of the average lattice strains to the active ions on the pulse shape and the far-field beam spreading of a Q-switched laser. Calculations are made for the Cr(3+): sapphire system. The dynamic behavior of laser divergence as the pulse develops is studied without and with an internal aperture. The results can be used to search for similar effects in lasers involving other ions, such as Ti(3+) and Cr(4+).     

Optimization of instrumental parameters of a near-field thermal-lens detector for capillary electrophoresis

The optical scheme of a near-field dual-beam mode-mismatched thermal-lens detector for capillary electrophoresis with a crossed-beam configuration employing a multimode HeCd laser (325 nm) as an excitation source was optimized. It is shown that a multimode laser can be successfully used as an excitation source in thermal lensing with minimal deviations in thermal responses from Gaussian excitation sources. An equation for diffraction thermal-lens theory for near-field measurements is deduced, and the experimental results agree with the deduced equation. The temperature rise in the capillary was estimated, and the exponential decrease of the signal with time for static conditions and low flow velocities was explained. The optimum configuration of the detector from the viewpoint of the maximum sensitivity and beam sizes was found. The detector provides a significant improvement in the detection limits for model compounds absorbing at 325 nm (nitrophenols) compared to the results obtained with a commercial absorbance detector operating at the same wavelength.     

Thickness optimization of the composite gain medium for the oscillator and amplifier of the lucia laser

Using a theory of quasi-three-level laser ions, we obtained the optimum thickness of the gain medium of Yb:YAG. For the parameters of the oscillator and the amplifier of the diode-pumped Lucia laser (Lasers Ultra-Courts et Intense et Applications), which will deliver a 100 J, 10 Hz, 10 ns pulse train the optimum thicknesses are, respectively, 1.4 and 1.6 mm, with a concentration of 10 at. %. Simulations indicate that the bending of such a thin medium is great but can be eliminated by substitution of a composite gain medium. The optimum thickness of undoped YAG is related to that of Yb:YAG and is also dependent on cooling conditions. Results show that, for a small-aperture oscillator, we can obtain both minimum bending and optical distortion at several doping concentrations. However, greater doping (approximately 20 at. %) is preferred for a large-aperture amplifier. The results reported will be helpful for the design of gain media for high-average-power thin disk Yb:YAG lasers.     

Tunable output power varying with the splitting ratio of a coupler from a fiber ring semiconductor laser

The tunable output power characteristics of a fiber ring semiconductor laser have been studied by use of rate equations. An expression for the tunable output power is deduced. The analysis confirms that there is an optimum coupler splitting ratio to trade off between wavelength tuning width and output power.     

Fragmentation of sialylated carbohydrates using infrared atmospheric pressure MALDI ion trap mass spectrometry from cation-doped liquid matrixes

Infrared atmospheric pressure matrix-assisted laser desorption/ionization on an ion trap mass spectrometer is used to study sialylated oligosaccharides desorbed from the liquid phase. Glycerol doped with various cations provides the opportunity to produce cation-adducted intact molecular ions of sugars. Distinct combinations of cations allow for sialic acid stabilization, as well as differential cleavage, resulting in more complete fragmentation coverage of the oligosaccharide. Alkali and transition metal cations are utilized to create three distinct molecular ion species, involving the adduction of a singly charged cation, two singly charged cations, or a doubly charged cation. From these different molecular ion types, complementary sequence, branching, and linkage information for sialylated oligosaccharides can be deduced.     

Application of mass spectrometry to the characterization of polymers

Recent advances in soft ionization techniques for mass spectrometry of polymeric materials make it possible to determine the mass of intact molecular ions exceeding 1 × 10⁶ Da. Developments in high resolution mass spectrometers have additionally led to impressive advances in our ability to characterize polymers. The entire molecular mass distribution of a polymer sample can be accurately measured. From the molecular mass, the molecular formulae and information regarding polymer composition and end-groups can be deduced. The two techniques which have received the most attention are matrix-assisted laser desorption/ionization and electrospray ionization. In recent work, these techniques have been combined with chromatographic separations, and a series of mass spectra are acquired for each fraction of the distribution. This simplifies the analysis by reducing the number of components present in each mass spectrum, and additionally improves quantitation.     

光纤阵列成像激光雷达系统的设计

简要介绍了光纤阵列成像激光雷达的研究背景、系统优势和发展现状.然后提出了本文设计的雷达系统,并介绍了该系统的工作原理,系统采用光纤阵列前端窗口扫描的方法,避免了光电探测器阵列的制作,同时减少了光电探测器的数量.之后文章对光纤阵列成像激光雷达系统的各部分器件进行分析,包括光纤的选择、光纤阵列的设计和聚焦透镜的分析,并重点讨论了聚焦透镜F值对光纤阵列接收系统的影响,最终得到本系统聚焦透镜F最优值5.47.最后推导了本文光纤阵列成像激光雷达系统的传输效率,给出了传输效率公式.