封离式He-N$lt;sub$gt;2$lt;/sub$gt;-CO$lt;sub$gt;2$lt;/sub$gt;激光器横模特性的测量与分析

利用激光光束分析仪,实时在线测量了一根He-N₂-CO₂封离式激光管的横模分布特性,得到了激光模式随放电电流的变化关系.实验表明该激光器在最佳工作电流时,容易形成低阶模运转,但很难获得基模运转,通过改善对称性以及加快冷却水流速可以获得基模运转.通过激光动力学过程分析了模式变化的形成原因,为大功率激光器模式控制与改善提供了一定的理论和实验借鉴. 关键词： 2激光')" href="#">CO₂激光 横模 激光模式分析 光束质量     

增益导波垂直腔激光器注入电流空间分布及其对激光近场模式影响的理论分析和表征

依据导电介质的稳态电场理论建立了一种对增益导波型垂直腔半导体激光器注入电流矢量分析的三维解析模型. 计算研究了电流密度空间分布及其与顶面电注入环参量之间的相互关联性. 结果显示在两极之间存在一个载流子径向分布中心极大的区域. 由于激光功率与注入电流之间存在线性关系,因此,要使器件能够获得基模或中心均匀的光强输出以及尽可能低的阈值,应使激光有源层与载流子均匀分布的临界层重合. 计算结果对顶发射与底发射结构以及不同环参数下的载流子分布情况及对近场模式形成的影响进行了分析和讨论. 关键词： 垂直谐振腔激光器 注入电流 激光模式     

激光陀螺谐振腔横模特征的测量与分析

为了判定被测激光的模式特征,基于激光的频率特性,提出了一种测量激光陀螺谐振腔横模特征的方法.利用F-P扫描干涉仪,可以实时在线测量激光模式分布特性,该方法以已知F-P扫描干涉仪的频率间隔和扫频速度为比例尺,将难以测量的横模频率间隔转化为易于测量的时间间隔,通过测量从扫描干涉仪给出的谱图,计算出不同横模的频率间隔与纵模间隔的比例系数,并与该陀螺的理论比例系数进行比较,从而实现对激光陀螺谐振腔横模特征的精确判定.通过对某型环形激光谐振腔的测量实验,得到了该陀螺模式特征随着工作电流大小变化的规律:随着放电电流的增加,激光陀螺腔内所振荡的横模由单一的基模逐渐转变为基模和高阶模的混合模,并准确地判定出该谐振腔横模特征,其测量结果与理论结果误差小于2%.利用该方法横模频率间隔测量准确度可达1 MHz,重复性可达0.4 MHz.     

激活介质热效应对振荡模式的影响研究

理论分析了激活介质热效应对端面泵浦固体激光器激光振荡模式分布的影响,并以光纤耦合半导体激光器端面泵浦Nd∶YAG激光器实验研究了激活介质热效应对激光振荡模式的影响。实验结果表明：由于热效应,基模的模体积随泵浦功率的增加而变大,基模在模式竞争中占优;在泵浦光轴线偏离几何腔轴时,基模光斑中心位置朝泵浦光轴线所在位置移动,偏离量与泵浦光轴线的偏离量近似成线性关系。利用实验结果指导腔调节,可使泵浦光轴线与几何腔轴精确重合,获得了椭圆率为0.98、M2因子为1.01的基模输出。     

轴对称-折叠组合腔CO_2激光器原理性实验研究(英文)

报道了轴对称-折叠组合腔CO2激光器原理性实验研究,激光器能在CW模式下成功运行。研究得到了激光器最佳的气体比率和气体压强。通过研究CO2激光器的不同方面,如激励门电压和输出功率等,发现它们随着放电电流的变化而变化。通过实验得到了激光光束的光斑和聚焦的实验光斑,并模拟了光强分布。激光器已经成功的组建、运行和调试,获得的最大输出功率为58 W。     

自由耦合输出的大模场面积光子晶体光纤锁模激光器

对一种基于高增益掺Yb³⁺大模场面积光子晶体光纤（PCF）的锁模激光器进行了简化线型腔结构的实验和理论研究.实验中直接使用塌陷打磨为0°角的光纤端面作为一端腔镜,利用其端面反馈获得了激光振荡,并进一步利用半导体可饱和吸收镜（SESAM）和光栅对的滤波作用实现了稳定的锁模运转.通过调节滤波程度,使激光器实现了从宽带滤波锁模到窄带滤波锁模的连续可调谐.在宽带滤波锁模的条件下,得到了最大平均输出功率2.2 W,单脉冲能量29.3 nJ,脉冲宽度367 fs的锁模脉冲输出;在窄带滤波锁模的条 关键词： 飞秒激光 光纤激光器 光子晶体光纤 大模场面积光纤     

直流激励慢速流动陶瓷放电管CO2激光器的实验研究

直流激励慢速流动陶瓷管CO_2激光器的基模功率较玻璃管激光器高45％。实验结果优于美国J.Macken分布型镀金薄膜对基模CO_2激光器的改善功能。文中还讨论了该激光器大幅度提高功率的机理。     

大模场面积光子晶体光纤激光器展宽脉冲锁模域的束缚态运转

实验研究了大模面积光子晶体光纤飞秒激光器在近零色散点展宽脉冲锁模的束缚态运转.获得了双脉冲束缚态锁模,以及脉冲间隔不相等的多脉冲束缚态锁模,实验发现束缚态的子脉冲间距具有随机性.通过建立光纤锁模激光器的数值模型,分析了激光器束缚态锁模建立的动力学过程,在一定抽运强度下,激光器存在多个稳态,或者单脉冲运转,或者子脉冲间隔不相等的束缚态运转,这取决于锁模建立阶段半导体可饱和吸收镜(SESAM)对噪声信号的随机提取.并提出了抑制束缚态的方法,模拟得出此项技术可直接获得的最大单脉冲能量为19.6 nJ,考虑到40%左右的压缩损耗,可得到压缩至76 fs的最短脉冲,单脉冲能量为11.8 nJ.数值模拟结果能很好的与实验相符合.     

高功率准连续波腔内和频全固态黄光激光器

报道了高功率准连续波腔内和频全固态黄光激光器的研究结果.为获得高功率的黄光输出,首先,激光器采用准连续方式运转,在保持抽运水平的条件下降低热效应,从而提高光束质量和光光转换效率;第二,采用热近非稳腔腔型设计,双棒串接补偿热致双折射技术,获得大基模体积高光束质量的基频光;第三,通过优化腔型,采用L型共折叠臂平-凹对称腔,使两束基频光达到空间重合且满足功率配比.通过这些方法,得到了输出功率7.6W,重复频率1.1kHz的准连续波黄光输出.据我们所知,这是目前腔内和频方案所获得的最高功率全固态黄光输出. 关键词： 黄光激光 腔内和频 Nd：YAG激光 全固态激光器     

LD抽运Cr,Tm,Ho∶YAG微片激光器单纵模运转特性的研究

研究了LD抽运的单纵模Cr,Tm,Ho∶YAG微片激光器,激光器厚度为1?mm,在用波长785?nm的LD进行端面抽运时,激光器阈值为1060?mW,单纵模激光最大输出功率为31?mW. 对激光器输出功率随温度变化特性进行了研究,验证了CTH∶YAG晶体的温度敏感性. 还研究了激光器的温度调谐特性,实验测得激光器的温度调谐系数为14?GHz/℃. 关键词： 激光光学 CTH∶YAG微片激光器 LD抽运 单纵模运转     

μ+SR study of LaNi2As2, URh2Si2 and CeRh2Si2

Muon spin relaxation experiments have been carried out in the paramagnetic and magnetically ordered states of URh₂Si₂ and CeRh₂Si₂. As the magnetic structure of these compounds is well known, these measurements can help to characterise their magnetic properties probed by μSR and to understand the μSR results of the heavy fermion compounds of the same crystallographic family. Our measurements show that the muons occupy two different crystallographic sites. The spectra of URh₂Si₂ and CeRh₂Si₂ in the magnetically ordered states are very different, probably reflecting their different magnetic structures. The spectra obtained on CeRh₂Si₂ are similar to the published spectra of the heavy fermion compound CeCu_2.1 Si₂. Muon spin rotation measurements on LaNi₂As₂ indicate that the muon is diffusing at 150 K.     

13C-selective IRMPD of CBr2F2/Cl2 and CCl2F2/Br2 systems

The CO₂ TEA laser irradiation of CBr₂F₂ in the presence of Cl₂ yielded ¹³C-enriched CBrClF₂ and ¹³C-enriched CCl₂F₂ under selected experimental conditions. As the photolysis proceeded, the ¹³C concentration of CBrClF₂ decreased gradually and that of CCl₂F₂ increased up to 90% or higher. These results can be explained by the mechanism involving the secondary ¹³C-selective IRMPD of the primary product CBrClF₂. On the other hand, the carbon-containing product for a CCl₂F₂/Br₂ system was only CBrClF₂; the further IRMPD of which probably regenerated CBrClF₂ in the presence of Br₂. The decomposition probabilities of ¹²C- and ¹³C-containing molecules in both systems were measured as functions of laser line, laser fluence, and reactant pressures.     

Magnetostriction of SmMn2Ge2 and GdMn2Ge2 intermetallic compounds

Longitudinal and transverse magnetostrictions of polycrystalline samples of intermetallic compounds RMn₂Ge₂ (R=Sm or Gd) are measured in pulsed magnetic fields up to 250 kOe. It is found that linear magnetostrictive strains of about 10^?3 arise in a temperature range in which the magnetic field causes a change in the magnetic state of a manganese magnetic subsystem. The results obtained are described within the model of a two-sublattice ferrimagnet with a negative exchange interaction in the manganese subsystem in terms of a strong dependence of this interaction on interatomic distances.     

Synthesis and properties of HgI2 intercalation of Bi2Sr2CaCu2Oy superconductor

Polycrystalline or single crystals of HgI₂ intercalated Bi₂Sr₂CaCu₂O_y (Bi2212) have been synthesized and their properties have been studied together with those of HgBr₂ intercalates. Single crystals of HgI₂ intercalated Bi2212 were synthesized by a stepwise intercalation method using iodine intercalate as a secondary host material. These could not be obtained through direct intercalation methods by which polycrystalline sample were obtained. From ac susceptibility and resistivity measurements, superconducting onset temperature (T_con) for polycrystalline HgI₂ intercalate was found to be 82 K which was higher than that of the host (75 K). On the other hand, T_con for single crystal HgI₂ intercalate was shown to be 79–80 K which is lower than that of host (95–97 K). The effect of HgI₂ or HgBr₂ intercalation on T_c tried discussion from the view point of hole doping and interblock coupling effect.     

Eu2+掺杂CaSi2O2N2荧光粉发光性能

采用固相反应法合成了组成为Ca_1-xEu_xSi₂O₂N₂的Eu²⁺掺杂CaSi₂O₂N₂荧光粉.通过荧光光谱对样品的发光性能进行了研究,发现Eu²⁺掺杂CaSi₂O₂N₂荧光粉发射光谱为宽波段的单峰结构,主要包含绿光和黄光区,发射峰在556~568 nm.从发射光谱的宽带特征来看,CaSi₂O₂N₂:Eu²⁺的发射主要对应着Eu²⁺离子4f⁶5d→4f⁷跃迁.从激发光谱所覆盖的范围还可以看到,样品可以有效的被UV蓝-光激发,这意味着该类荧光粉在白光LED方面有可能得到广泛的应用.另外,样品的发光性能与激发离子的浓度有着很大关系.激发离子浓度增大时,发射光谱会发生明显红移.利用这一性质,可以通过改变Eu²⁺浓度来调节荧光粉的发光范围,从而满足不同场合的需要.同时,Eu²⁺浓度提高,样品发射光谱的强度也会随之增强,在x=0.06时发射强度达到最大值,之后继续增加Eu²⁺浓度,强度不仅没有增加反而降低,即出现浓度猝灭现象.     

X-ray photoemission spectra measurements of CeNi2Sb2 and CeCu2Sb2

X-ray photoemission spectra, resistivity and susceptibility of CeNi₂Sb₂ and CeCu₂Sb₂ were measured and are discussed. The results indicate that these alloys are Kondo systems. For comparison of the valence band properties, the spectra of the isostructural alloys of RT₂X₂-type with R = La, Gd, T = Cu, Ni and X = Sn, Sb were investigated, too.     

(NH_2CH_2COOH)_2CdCl_2晶体的拉曼光谱的研究

（ＮＨ２ＣＨ２ＣＯＯＨ）２ＣｄＣｌ２晶体的拉曼光谱的研究刘建军吴粤郑吉民扈士芬蓝国祥（南开大学天津３０００７１）ＲａｍａｎＳｐｅｃｔｒａｏｆ（ＮＨ２ＣＨ２ＣＯＯＨ）２ＣｄＣｌ２ＣｒｙｓｔａｌｓＬｉｕＪｉａｎｊｕｎ，ＷｕＹｕｅ，ＺｈｅｎｇＪｉｍｉｎ，Ｈ...     

CO2-laser-induced multiphoton absorption of CF2Cl2

Energy absorption by CF₂Cl₂ from an intense TEA CO₂ laser pulse is measured as a function of the pressure of CF₂Cl₂ and the pressure of Ar bath gas for different laser energy fluences. The fraction of the molecules excited by the laser field and the average energy of the molecular ensemble are determined by a simple experimental method.