新型Q开关晶体Cr4+∶YAG的生长和退火研究

采用二价Ca离子作为电荷补偿离子由提拉法生长出了具有高光学质量的调Q开关晶体Cr4+∶YAG并对该晶体进行了退火研究.吸收光谱测量表明原生态晶体中已有少量Cr4+离子存在.晶体经空气中退火后Cr4+离子浓度和1.06μm处的吸收系数均显著提高.晶体生长和退火实验显示出晶体中Cr4+离子的浓度不仅取决于掺杂的Cr3+离子的浓度,而且同晶体中的Ca/Cr浓度比密切相关.     

导模提拉法生长Tb3Sc2Al3O12(TSAG)晶体及性质表征

本文采用导模提拉法成功生长了Tb3Sc2Al3O12 (TSAG)晶体,并对所生长晶体进行了物相分析和单晶结构分析,探讨了多晶原料的烧结温度对晶体颜色的影响.Sc3+和Al3+的浓度分布测试表明,导模提拉法能较好地克服因分凝效应引起的Sc3+浓度分布不均,可以生长获得浓度分布均匀的TSAG晶体.磁光性能测试表明,Sc3+掺入对晶体在400～1100 nm波长范围内的磁光性能影响不大,所生长TSAG晶体的费尔德常数仅比Tb3Al5O12 (TAG)晶体低6; ～8;.     

掺杂GSGG激光晶体热导率研究

为研究不同掺杂GSGG激光晶体的导热特性,用瞬态脉冲法测量了273～393K温度范围内自己生长的Cr:GSGG、Nd,Cr:GSGG和Nd:GSGG激光晶体热导率.建立了实验样品温度场模型,推导出晶体热导率随温度升高呈下降变化趋势的结论,这与实验测量结果基本相符,通过对测量结果曲线拟合给出了拟合方程.并从理论上解释了掺入较高浓度的杂质Cr3+离子会使得晶体的热导率值有所降低,以及双掺Nd3+、Cr3+离子和单掺Nd3+离子的GSGG晶体热导率值基本相同的原因.     

Yb3+:YVO4晶体的生长及光谱性能研究

采用提拉法生长出光学质量优良的Yb3+:YVO4晶体,研究生长过程中工艺参数的控制.测得掺杂浓度为18.1;Yb3+:YVO4晶体中Yb3+离子的有效分凝系数Keff为0.96.测定了不同Yb3+离子掺杂浓度晶体的吸收光谱和荧光光谱,并分别计算了不同掺杂浓度下Yb3+:YVO4晶体的光谱参数.本文总结和解释了掺杂浓度影响其性能的规律,讨论了Yb3+:YVO4晶体作为激光晶体的优点.     

Cr3+:BeAl2O4单晶的特性及生长工艺的改进

描述了掺Cr3+离子的紫翠宝石(Cr3+:BeAl2O4)单晶的晶体结构、物理性质、晶体的吸收光谱与发射光谱及其激光特性.讨论了用引上法生长Cr3+:BeAl2O4晶体的一些工艺问题中.引上法晶体生长过程中选用较慢的提拉速度、较快的转速和生长较大直径的晶体的工艺参数,能够生长出高质量的Cr3+:BeAl2O4单晶体.我们的实验表明,采用温梯法也能生长出高质量的Cr3+:BeAl2O4单晶.与提拉法相比,温梯法减少了原料对环境的污染;易于实现自动温度程序控制;对缺少自然对流的熔体有相当好的适用性.     

Cr:iSrAlF6晶体生长及其性能表征

本文报道了布里奇曼法生长的高品质Cr:iSrAlF6 晶体及其激光特性.采用固相氟化反应除去原料中的氧化物和水.在较小的温度梯度和较慢的生长速率下生长出的Cr:iSrAlF6晶体尺寸达到φ20mm×130mm.均匀的Cr3+掺杂浓度为1～15mol;.从XRD谱图计算出的Cr:iSAF晶体点阵参数为a=0.502nm,c=0.967nm.测试了晶体的吸收曲线,并分析了其吸收与能带结构的关系.实现了闪光灯泵浦的Cr:iSAF激光器运转,激光转换斜效率达到5.85;.     

Cr4+,Yb3+:YAG晶体的生长及其吸收特性

用提拉法生长了Cr,Yb:YAG晶体,研究了在室温的吸收光谱特性以及氧化性气氛退火对其吸收特性的影响.在室温吸收光谱中存在着五大吸收带:在440nm和605nm存在着Cr3+离子的两个吸收带,而且退火使其发生了明显的"红移";在937nm和968nm处存在Yb3+离子的两个吸收带,能与InGaAs激光二极管(LD)有效耦合,适合激光二极管泵浦;而且在1.03μm处有一Cr4+离子的吸收峰,可用作可饱和吸收体,从而可以实现对Yb3+的自调Q激光输出.在氧化性气氛下退火对晶体吸收特性及缺陷的影响是:退火使晶体的缺陷明显减少而且使Cr4+浓度得到进一步的增加;Cr4+离子浓度的增加主要是由于二价阳离子Ca2+进入相应的Y3+晶格所造成.并且从晶格场的角度讨论了退火使Cr3+离子的吸收带发生"红移"的原因.     

Cr:LiSrAlF_6 晶体生长及其性能表征(英文)

本文报道了布里奇曼法生长的高品质Cr:LiSrAlF6晶体及其激光特性。采用固相氟化反应除去原料中的氧化物和水。在较小的温度梯度和较慢的生长速率下生长出的Cr:LiSrAlF6晶体尺寸达到2 0mm× 130mm。均匀的Cr3 +掺杂浓度为 1～ 15mol%。从XRD谱图计算出的Cr:LiSAF晶体点阵参数为a =0 .5 0 2nm ,c =0 .96 7nm。测试了晶体的吸收曲线 ,并分析了其吸收与能带结构的关系。实现了闪光灯泵浦的Cr:LiSAF激光器运转 ,激光转换斜效率达到 5 .85 %。     

Cr2+∶ZnSe中红外激光晶体生长及光谱性能

采用物理气相输运法( PVT),以Cr2+∶ ZnSe多晶为原料,在源区温度约为1000℃、温差为6～7℃条件下生长2周,获得了体积约为0.7 cm3的Cr2+∶ZnSe晶体.紫外-可见-近红外透过光谱显示,Cr2+∶ZnSe样品在1770nm左右出现了强吸收;Cr2+浓度在1019 atoms/cm3数量级,与原料中Cr2+浓度基本一致,反映了较低温度PVT法生长有利于获得预期的Cr2+掺杂浓度.荧光测试结果表明,Cr2+∶ZnSe样品谱线对称性好,发射峰位约在2400 nm,线宽约600 nm;室温荧光寿命为5.52×10-6s.数据分析结果表明,Cr2+∶ZnSe样品的吸收截面和发射截面峰值分别为1.1×10-18cm2和2.3×10-18 cm2.     

EDTA和KCl掺杂对KDP晶体光学质量的影响

通过传统降温法生长了不同EDTA和KCl剂量掺杂的KDP晶体,并观察了晶体的光散射情况,测定了晶体柱区样品的透过率和晶体中Fe、Cr、Cl三种杂质元素的含量,结果表明:低浓度的EDTA(0.01 mol;)和KCl(＜1.5 mol;)掺杂可以提高晶体的透过率,但高浓度掺杂(0.01 mol;EDTA, 2.0 mol; KCl)会导致晶体散射严重,透过率降低,KCl浓度达到2.5 mol;后晶体生长受到抑制,晶体缺陷严重;晶体中铁Fe3+、Cr3+的总含量随着掺杂浓度的增加而减少,晶体中并没有发现Cl元素存在.     

MgAl2O4:Cr3+单晶光纤生长与荧光温度特性研究

采用激光加热基座法制备了0.5at;Cr3+掺杂镁铝尖晶石单晶光纤.通过XRD、荧光光谱、荧光寿命测试对所制备的单晶光纤的晶相、荧光温度特性进行了实验研究,结果表明所制备的MgAl2O4:Cr3+单晶光纤的主晶相为MgAl2O4晶相,镁铝尖晶石晶相结构并没有因Cr3+掺入而发生改变,在405nmLED激发下,随着温度升高MgAl2O4:Cr3+单晶光纤荧光强度下降,尤其是2E→4A2能级跃迁产生的荧光强度下降明显,同时随着温度的升高,MgAl2O4:Cr3+单晶光纤的荧光寿命随温度单调下降,系统荧光寿命从室温293K的7.74ms下降到723K的0.5ms左右.由于其相对较长的荧光寿命,MgAl2O4:Cr3+单晶光纤非常适合作为荧光温度敏感材料应用于荧光寿命型光纤温度传感器.     

Cr,Nd:GSAG晶体生长、光谱及LD泵浦激光性能研究

Cr,Nd:GSAG是一种性能优良的激光晶体,但是关于它的LD泵浦激光性能的研究很少.用提拉法生长了Cr,Nd:GSAG晶体,测定了它的化学成分、结构,初步测试了它的激光性能.晶体的(111)面X射线摇摆曲线半高全宽为0.055°.采用Rietveld方法精修X射线粉末衍射谱得到了Cr,Nd:GSAG晶体的原子结构参数、温度因子等.Cr,Nd:GSAG的最强吸收峰位于808.6nm处,吸收截面为3.38×10-20cm2.808nm光激发下,Cr,Nd:GSAG的最强发射峰位于1060nm,发射截面为6.04×10-20cm2,并测得激光上能级4F3/2的荧光寿命为274μs.利用808nm连续波LD泵浦实现了1060nm的激光输出,在输入功率为8.88W时,最大输出功率为0.513W,斜效率为6.73;,光-光转换效率为5.78;.此外还讨论了Cr,Nd:GSAG晶体中的Cr3+与Nd3+之间的能量传递机理.     

复合晶核剂对黄磷炉渣微晶玻璃析晶的影响

以黄磷炉渣为主要原料,通过添加不同种类的复合晶核剂,采用熔融法制备了黄磷炉渣微晶玻璃.借助化学热力学软件FactSage 6.4模拟计算晶相类型,借助Kissinger方程分析析晶能力,利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)进行验证.结果表明:相比添加单一晶核剂TiO2,复合晶核剂TiO2+CaF2或复合晶核剂TiO2+P2O5均能够降低黄磷炉渣基础玻璃的析晶活化能E,促进其析晶,复合晶核剂TiO2+Cr2O3能够提高黄磷炉渣基础玻璃的析晶活化能E,抑制其析晶;无论添加单一晶核剂TiO2,还是添加复合晶核剂TiO2+CaF2、复合晶核剂TiO2+P2O5或复合晶核剂TiO2+Cr2O3,黄磷炉渣微晶玻璃晶相类型相同,主晶相为硅灰石(CaSiO3),副晶相为铝透辉石(Ca(Mg,Al)(Si,Al)2O6)和氟磷灰石(Ca5(PO4)3F),这与化学热力学软件FactSage 6.4模拟计算结果基本一致.     

Recharging processes of Cr ions in Mg2SiO4 and Y3Al5O12 crystals under influence of annealing and γ ‐ irradiation

Recharging processes of chromium ions were investigated for Mg₂SiO₄:Mg, Cr single crystals using annealing in O₂ and in air and γ‐irradiation, as compare to YAG :Ca, Cr single crystals. The formation of tetravalent Cr ions in the Mg₂SiO₄ :Mg, Cr is related not only to the initial Cr content in the melt, oxygen partial pressure and O₂‐ vacancy existing in the crystal, but also to the external field such as γ‐irradiation. The additional absorption after γ‐irradiation shows the decrease in intensity of the absorption of Cr³⁺ and Cr⁴⁺ ions in some part of the spectrum and increase in the other giving evidence on recharging effects between Cr³⁺ and Cr⁴⁺. There arises also color centers observed between 380 nm and 570 nm that may participate in energy transfer of any excitation to Cr⁴⁺ giving rise to Cr⁴⁺ emission. Opposite to forsterite crystal, absorption spectrum of YAG:Ca, Cr crystal after γ‐irradiation reveals only increase in the absorption of the Cr bands. The observed behavior of the absorption spectrum of YAG:Ca, Cr crystal under influence of γ‐irradiation suggests that γ‐irradiation ionizes only Cr ions. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and properties of (Cr, Nd) doped GdCa4O(BO3)3 crystals

Optical quality Nd:GdCa₄O(BO₃)₃ (Nd:GdCOB) crystal and chromium sensitized crystal of Cr:Nd:GdCa₄O(BO₃)₃ (Cr:Nd:GdCOB) were grown by the Czochralski (CZ) method. The transmittance spectra was measured at room temperature on 7at%Nd:GdCOB and lat%Cr:7at%Nd:GdCOB samples. The absorption in the blue-UV region of Cr:Nd:GdCOB was larger than that of Nd:GdCOB, which matched the xenon flash lamp very well. A 3×3×10mm³ Nd:GdCOB sample without any antireflective coating was sidepumped using a pulsed dye-laser tuned to 595.4nm. The green-light output energy was 1.35mJ at a pump energy of 17.5mJ. The conversion efficiency was 7.7%, and the threshold energy was less than 1.2mJ which are the best results up to now to our knowledge. 3×3×7mm³ Nd:GdCOB and Cr:Nd:GdCOB samples without antireflective coatings were pumped using a flash pump source. The threshold for Cr:Nd:GdCOB was 0.9J while for Nd:GdCOB it was I.O.J. The output green light energy was 2.46mJ for Cr:Nd:GdCOB at a 10J flash pump energy and was 1.96mJ for Nd:GdCOB at the same pump energy, which clearly shows that Cr³⁺ ions have the sensitizing effect on the Nd³⁺ ions in Nd:GdCOB crystal.     

Distribution of metallic ions in a single KDP crystal grown from aqueous solution

A single KDP (potassium dihydrogen phosphate) crystal was grown in a supersaturated solution containing a metallic ion (Al³⁺, Fe³⁺, or Cr³⁺). The growth rate, morphology, and distribution of the metallic ions into the KDP crystal were measured as the ionic concentration and supersaturation in the solution changed. It was found that in the KDP crystal, Al³⁺ and Fe³⁺ were greatly concentrated, but Cr³⁺ was diluted. Complete expressions for the effect of metallic ions on all aspects of the growth of KDP crystal were suggested. The growth rates of (100) and (101) faces were well correlated by the empirical equation and resulted in good estimation of morphology. The distribution of metallic ions into KDP crystal was also correlated by the distribution model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

一族Nd:YxGd1-xVO4混晶性质比较及其调Q性能研究

Czoehralski法成功生长了一系列不同Cd／Y的低掺杂Nd：YxGd1-xVO4混晶，并对它们的一些基本性质进行了比较，发现随着Gd含量的增加，晶体晶胞a，c轴常数呈线性增长，故YVO4和GdVO4晶体可以实现无限互溶。少量Gd掺杂可使混晶晶体比热和荧光寿命增大，并有效地增强了其荧光强度。我们对该晶体的低功率泵浦下的Cr^4 ：YAG调Q激光性能也进行了研究，发现Nd：YxGd1-xVO4混晶具有良好调Q性能。     

Distribution of oxidation states of Cr ions in Ca or Ca/Mg co-doped Cr:Y3Al5O12 single-crystal fibers with nitrogen or oxygen annealing environments

The valence states of Cr ions in Ca or Ca/Mg co-doped Cr:Y₃Al₅O₁₂ (YAG) single-crystal fibers are studied. The fibers were grown using the laser-heated pedestal growth method, followed by annealing treatments up to 1500 °C. The concentrations of the Cr³⁺ and Cr⁴⁺ ions in octahedral and tetrahedral sites in oxygen or nitrogen environments were characterized. Above 700 °C, migration of Cr⁴⁺ between octahedral and tetrahedral sites takes place; its relative stabilization energy was estimated. For Ca,Cr:YAG annealed in an oxygen or nitrogen environment, it was 0.25 and 0.3 eV, respectively. For Mg,Ca,Cr:YAG annealed in oxygen or nitrogen, it was 0.47 and 0.49 eV, respectively. For the Ca,Cr:YAG crystal fiber (Ca/Cr=113.1%) with oxygen annealing, about 35% and 2.5% of Ca ions took part in charge compensation for Cr⁴⁺ in the octahedral and tetrahedral sites, respectively. The density of oxygen vacancies depends on the concentration of Ca ions. The estimated ratios of the unreacted oxygen vacancies to total oxygen vacancies were about 63% and 88% for oxygen and nitrogen annealing, respectively. The main limitation on the concentration of Cr⁴⁺ in the tetrahedral site of YAG is the presence of unreacted oxygen vacancies.     

双温区热扩散掺杂Fe2+∶ZnSe激光晶体的制备及激光输出性能

本文以CVD ZnSe晶片为基质材料,以FeSe粉末为掺杂物,采用双温区热扩散掺杂技术获得了尺寸为Ø22 mm×4 mm的Fe²⁺∶ZnSe激光晶体。通过二次离子质谱(SIMS)测试该晶体样品表面铁离子浓度为3.43×10¹⁸ cm^-3,并通过X射线光电子能谱(XPS)分析了晶体样品中铁元素的离子价态。采用UV/Vis/NIR分光光度计和傅里叶红外光谱仪测试了Fe²⁺∶ZnSe激光晶体的透过谱图。测试结果显示,在3.0 μm处出现了明显的Fe²⁺吸收峰,峰值透过率为5.5%。以波长为2.93 μm的Cr, Er∶YAG激光器为泵浦源,温度77 K时抽运尺寸10 mm×10 mm×4 mm的 Fe²⁺∶ZnSe晶体,获得了能量为191 mJ、中心波长4.04 μm的中红外激光输出,光光转换效率13.84%。