Yb3+掺杂KY(WO4)2激光晶体生长、结构与光谱分析

采用顶部籽晶提拉法(TSSG)生长出Yb:KY(WO4)2(Yb:KYW)激光晶体.对预烧后的原料及晶体进行了XRD分析,结果表明,分别在920℃和600℃预烧8h后的熔质和助熔剂基本上形成一相,抑止了实验中的挥发问题;所生长的晶体为β-Yb:KYW,计算其晶格常数为a=1.063nm,b=1.034nm,c=0.755nm,β=130.75°.测得不同厚度样品的吸收光谱,结果表明样品在933nm和981nm有较强的吸收峰,计算出主峰981nm的吸收截面σabs=5.34×10-20cm2.测得样品的荧光光谱,计算出主峰1030nm受激发射截面σem=3.1×10-20cm2,并估算其荧光寿命为0.56ms,与实测值0.60ms吻合.计算出激发态最小粒子数(β)、饱和抽运强度(Isat)和最小抽运强度(Imin),通过与其他掺Yb3+晶体比较,结果表明Yb:KYW晶体的Imin(0.24kW/cm2)很小.     

新型激光晶体Yb:KY(WO4)2的结构与光谱

采用顶部籽晶提拉法，以K₂W₂O₇为助溶剂，生长了Yb:KY(WO₄)₂新型激光晶体.经热重-差热分析，确定晶体熔点为1045℃，相变温度为1010℃.X射线粉末衍射测试，验证所生长的晶体为β-Yb:KY(WO₄)₂.晶体结构分析确定Yb:KY(WO₄)₂晶体由WO₆八面体连接而成，WO₆八面体是由双氧桥(WOOW)及单氧桥(WOW)构成.晶体粉末样品室温下的红外及拉曼光谱测试，确定WO₆原子基团、双氧桥及单氧桥的振动频率.晶体的吸收峰位于940nm，980nm，发射峰位于989nm—1030nm. 关键词： 晶体结构 光谱 晶体生长     

Pr,Yb,Ho:GdScO3晶体生长及光谱性能

2.7—3.0μm波段激光在很多领域具有重要应用,为探索和发展该波段新型晶体材料,本文采用提拉法生长出Pr, Yb, Ho:GdScO₃晶体,通过共掺入Pr³⁺离子以达到衰减Ho³⁺:⁵I₇能级寿命的目的.采用X射线衍射测试得到了晶体的粉末衍射数据,测量了拉曼光谱,并对晶体的拉曼振动峰进行指认,对Pr, Yb, Ho:GdScO₃晶体的透过光谱、发射光谱和荧光寿命进行表征. Yb³⁺的最强吸收峰在966 nm,吸收峰半峰宽为90 nm;2.7—3.0μm波段最强发射峰在2850 nm,半峰宽为70 nm; Ho³⁺:⁵I₆和⁵I₇能级寿命分别为1094μs和56μs.与Yb,Ho:GdScO₃晶体相比, Yb³⁺的吸收峰和2.7—3.0μm的发射峰半峰宽明显展宽,同时下能级寿命显著减...     

Tm:Y2SiO5晶体的生长和光谱性质研究

采用中频感应提拉法生长了高质量的Tm:Y₂SiO₅(Tm:YSO)晶体,测定了晶体的晶格常数和分凝系数.运用劳厄照相法确定了单斜晶系Tm:YSO晶体的三个偏振轴〈010〉,D₁和D₂,在室温下测量了三个偏振轴方向的吸收光谱、荧光光谱和荧光寿命,计算了晶体吸收峰的吸收线宽和吸收截面.研究发现,相对于其他两个偏振轴方向,D₁方向在790nm处出现较强的吸收峰, 关键词： 2SiO₅')" href="#">Tm:Y₂SiO₅ 单斜晶系 吸收光谱 荧光光谱     

MgF2单晶的THz光谱研究

利用THz时域光谱技术对MgF₂晶体(样品1)和MgF₂：Co晶体(样品2)在0.5—2.5 THz的吸收特性进行了研究.在0.5—2.5 THz波段，样品1吸收系数α(ν)随频率ν增加而增大，最大值为24 cm^-1.样品2的吸收系数比样品1大得多，Co掺杂使晶格吸收带边向低频移动，而且样品2在1.9 THz有吸收峰，吸收系数达到70 cm^-1，由此求出F^--Co²⁺离子键伸缩振动的键力常数K为3.40×10^-2　N/cm.这一结果表明，THz光谱分析有可能成为研究晶体化学键的一种重要手段.利用光学常数之间的关系计算了两个样品在0.5—2.5 THz的介电函数的实部ε₁(ν)，得到样品1的ε₁(ν)值在4.67至4.73之间，样品2的ε₁(ν)值在4.62至5.01之间. 关键词： THz辐射 光谱 2晶体')" href="#">MgF₂晶体     

Yb:CaYAlO4再生放大器

阿秒科学是驱动超强超快激光往高平均功率和短脉冲宽度方向快速发展的动力之一.本文针对高重复频率阿秒光源的实际需求,开展了基于国产Yb:CaYAlO₄晶体的再生放大理论和实验研究.在理论研究中,根据Yb:CaYAlO₄晶体的热透镜计算结果,设计了热稳定性良好的模式可调再生腔;并对晶体π和σ偏振的放大输出能量和光谱进行计算.在此基础上,开展了Yb:CaYAlO₄晶体不同偏振性质的再生放大实验研究.在晶体π偏振的实验中,获得了平均功率16.1 W、单脉冲能量1.61 mJ、光谱中心波长1030 nm、光谱半高全宽16 nm的放大输出,压缩后的激光脉冲宽度为149 fs,压缩效率为92.1%,峰值功率大于9.5 GW.在σ偏振获得了平均功率28.7 W、单脉冲能量2.87 mJ、光谱中心波长1037 nm、光谱半高全宽11 nm的放大输出,压缩后的激光脉冲宽度为178 fs,压缩效率为91.5%,峰值功率大于14.2 GW,光束质量因子M² <1.2.以上研究结果实现了目前Yb:CaYAlO_4...     

Ti: LiAlO2新型晶体的结构分析

通过研究提拉法生长的掺杂Ti浓度为0.2at%的LiAlO₂晶体吸收光谱，荧光光谱和红外光谱，来分析此新型晶体的结构.分析发现光谱中仅出现了四价Ti离子的196nm的特征吸收峰, 用235nm光激发得到384nm的特征发射峰；针对吸收光谱中660—820nm出现的四个弱小吸收峰提出了一个色心模型，从而解释了空气和富Li气氛处理后吸收峰消失的现象；对比纯LiAlO₂晶体的红外光谱发现，Ti的掺入仅影响了［AlO₄］键强，而［LiO_{4 关键词： 2}')" href="#">Ti: LiAlO₂ 色心 光谱     

BaWO4∶Eu3+红色荧光粉的水热制备及其发光性能

采用水热法,通过变化水热反应时间制备出不同的BaWO₄∶Eu³⁺样品,利用XRD和SEM分析了样品的晶体结构和表面形貌,研究了基质晶体生长取向对BaWO₄中Eu³⁺离子特征发射的影响。实验结果表明:BaWO₄∶Eu³⁺样品在395 nm近紫外光或464 nm蓝光激发下发射578,592,612 nm的红光,其中612 nm(⁵D₀→⁷F₂)发射强度明显高于592 nm (⁵D₀→⁷F₁)。在水热温度160 ℃的情况下,所制备的样品均为四方相,不同的水热反应时间将影响晶体在各晶向的生长速度,进而影响晶体的对称性和发光性能。水热时间为10 h时的发射强度最大。     

不同Yb掺杂量的Yb:Y3Al5O12晶体的光谱分析

采用提拉法生长了Yb³⁺掺杂量分别为5.4at%, 16.3at%, 27.1at%, 53.6at%和100at%的Yb:Y₃Al₅O₁₂晶体.系统地表征和分析了Yb³⁺掺杂量对晶体吸收光谱和荧光光谱的影响.随着Yb³⁺掺杂量的增加，各峰值吸收系数呈线性增加的趋势.应用Smakula公式计算了各吸收峰对应的振荡强度，并分析了Yb³⁺掺杂量对振荡强度的影 关键词： 吸收光谱 荧光光谱 自吸收 浓度猝灭     

中子探测晶体Li6Gd(BO3)3:Ce的光谱特性研究

文章用提拉法生长出Li₆Gd(BO₃)₃:Ce晶体,并对其光谱性能与发光过程进行了探索. 借助于真空紫外-紫外透过光谱测试,发现晶体的透过光谱中存在Ce³⁺离子和Gd³⁺的特征吸收峰,同时还存在与Ce⁴⁺离子相关的电荷迁移带. 对晶体的真空紫外-紫外激发发射光谱进行研究发现,在晶体存在着Ce³⁺离子的5d→4f辐射跃迁发光与Gd³⁺离子的4f→4f辐射跃迁发光,而且存在着Gd³⁺→Ce³⁺之间的能量传递. 对Li₆Gd(BO₃)₃:Ce晶体的X射线与γ射线激发发射光谱研究可知,晶体在高能射线激发下的闪烁光主要是Ce³⁺离子的发光. 关键词： 6Gd(BO₃)₃:Ce晶体')" href="#">Li₆Gd(BO₃)₃:Ce晶体 真空紫外-紫外透过光谱 真空紫外-紫外激发发射光谱 能量传递     

Group delay dispersion measurement of Yb:YAl3(BO3)4 crystal with white-light interferometry

We report the group delay dispersion of Yb³⁺:YAl₃(BO₃)₄ (Yb:YAB) crystal measured by a white-light interferometer, and compare with that calculated from the Sellmeier formulae provided by the crystal supplier, over the wavelength range from 1000 nm to 1080 nm. The data should be useful for the dispersion compensation for femtosecond pulse generation in Yb:YAB lasers.     

Conversion of infrared radiation into visible emission in NaY(WO4)2:Yb, Ho crystal

The spectroscopic characteristics and fluorescence dynamics for Yb³⁺/Ho³⁺:NaY(WO₄)₂ crystal were investigated. The parameters of oscillator strengths, the spontaneous transition probabilities, the fluorescence branching ratios, the radiative lifetimes and the stimulated emission cross sections have been calculated based on Judd-Ofelt theory and Füchtbauer-Ladenburg method. The energy transfer efficiency from Yb³⁺ to Ho³⁺ was 65.85%. The green emission (530-570 nm) corresponding to (⁵F₄, ⁵S₂)→⁵I₈ transition, red emission (640-670 nm) due to ⁵F₅→⁵I₈ transition and NIR emission (740-770 nm) attributed to (⁵F₄, ⁵S₂)→⁵I₇ transition were observed on 974 nm excitation at room temperature. Under low pump power, the intensity of green light emission is weaker than that of the red light, while under high pump power, the case is on the contrary. The upconversion is based on the two-photon process either the energy transfer from Yb³⁺ ions or by the excited state absorption. The proposed mechanisms of upconversion emissions were provided.     

Green and red up-conversion emissions of Er-Yb-codoped Al2O3 powders prepared by the nonaqueous sol-gel method

The 1 mol% Er³⁺- and 0-20 mol% Yb³⁺-codoped Al₂O₃ powders have been prepared by the nonaqueous sol-gel process using aluminum isopropoxide as precursor, acetylacetone as chelating agent, nitric acid as catalyzer, and hydrated erbium and ytterbium nitrate as dopant under isopropanol environment. The two crystalline types of doped Al₂O₃, γ and θ, and a stoichiometric compound, (Yb,Er)₃Al₅O₁₂, were obtained for all the Er³⁺-Yb³⁺-codoped Al₂O₃ powders at the sintering temperature of 1000 °C. The maximal intensity of both the green and red up-conversion emissions centered at about 523, 545, and 660 nm was observed for the 1 mol% Er³⁺- and 10 mol% Yb³⁺-codoped Al₂O₃ powders. The intensity ratio of the red to green up-conversion emission (I_red/I_green) increased with increasing the Yb³⁺ doping concentration for the Er³⁺-Yb³⁺-codoped Al₂O₃ powders. Furthermore, the intensity ratio of the green up-conversion emission at about 523 to 545 nm (I₅₂₃/I₅₄₅) was proportional to the Yb³⁺ doping concentration and pump electric current, which was associated with the elevated temperature of powders.     

Influence of pump wavelength on the laser performance of Yb:KLu(WO4)2 crystal

By employing a tunable Ti:sapphire laser, we conducted an investigation into the effects of pump wavelength deviation on the laser performance of Yb:KLu(WO₄)₂ crystal. Pumping efficiencies exceeding 70% could be reached under lasing conditions with a 3-mm crystal of Yb concentration of 5.24 at.%, when the pumping wavelength was within the main absorption band centered at 981 nm extending from 974 to 990 nm. For different pumping wavelengths, the laser exhibited a single output–input relation with respect to absorbed pump power, giving an average slope efficiency amounting to 51%.     

Y2O3:Yb3+,Tm3+纳米材料的可见及紫外上转换发光

通过燃烧法制备了Yb³⁺-Tm³⁺共掺的Y₂O₃纳米粉体,并对样品在980 nm激光照射下的上转换发光特性进行了研究.实验发现,样品在可见光区域能够产生强烈的蓝色发光(476 nm和487 nm)和较弱的红色发光(约650 nm),而且同时观察到了两个紫外发光峰¹I₆→³H₆ (~297 nm)和^{1关键词： 2O₃:Yb3+')" href="#">Y₂O₃:Yb3+ 3+}')" href="#">Tm³⁺ 上转换光谱 敏化 紫外发光     

Origin of the 330 nm absorption band and effect of doping Yb in LiYF4 crystals

The electronic structures of LiYF₄ (YLF) crystals containing F color center (YLF-F) and Yb doped YLF crystals (Yb³⁺:YLF, Yb²⁺:YLF) are systematically studied within the framework of the density functional theory. The calculated results indicate that the 330 nm absorption band originates from the F center in YLF crystals. Thus the doping of Yb³⁺ can weaken the 330 nm absorption band by competing with F vacancies in capturing free electrons arising after γ-irradiation and change to Yb². By analyzing the lattice relaxation and the electronic structure of YLF containing Yb²⁺, we can reasonably believe that once Yb²⁺ is formed in YLF crystal, its compensating hole will turn out to be shared by two F⁻ nearest to Yb²⁺ forming a diatomic fluoride molecular ion () perturbed by Yb²⁺, or to say V_F color center. According to the molecular-orbital linear combination of atomic orbital (MO-LCAOs) theory, compared to the alkali halides, e.g. LiF, the in V_F center in LiYF₄ peaks at about 340 nm, which is in agreement with the experimental results.     

Optical character of Er/Yb co-doped P2O5-CaO-Na2O-Al2O3-AgO phosphate glass

The up-conversion (UC) and near infrared (NIR) luminescence of Er³⁺/Yb³⁺ co-doped phosphate glass are investigated. In the UC emission range, the 523 nm, 546 nm green emissions and the 659 nm red emission are observed. With the increasing pump power, the intensity ratios of I₅₂₃/I₆₅₉, I₅₄₆/I₆₅₉ and I₅₂₃/I₅₄₆ increase gradually. The phenomenon is reasonably interpreted by theoretical analysis based on steady state rate equations. The emission cross section of the infrared emission at 1546 nm is larger (about 6.7 × 10^− 21 cm²), which is suitable for making fiber amplifier.     

Theoretical investigation on thermal lensing effects of Yb:KY(WO4)2 in diode-pumped lasers

Based on the features of laser diode end-pumped lasers, a thermal model of Yb:KY(WO₄)₂(Yb:KYW) with square cross-section was established. Considering the heat transfer on side faces, the anisotropic of thermal conductivity and the latest reports about thermo-optic coefficient, thermal expansion coefficient and thermal conductivity, temperature distribution, end-pumped face distortion and thermal lens focal length of Yb:KYW were more precisely obtained using finite difference method to solve Poisson equation in a rectangular Cartesian coordinate for the first time. At the pump power of 14 W, the highest temperature located at the center of end-pumped face was 243.8 °C, the highest distortion was 0.28 μm, and the thermal lens focal length was 5.4 cm along z-axis and −4.9 cm along x-axis. The results show that thermal lensing effects in the b-cut Yb:KYW were mainly determined by the anisotropic thermal expansion of Yb:KYW, and further present thermal lensing effects become weaker after considering the heat transfer. This work is significant for compensating the thermal lensing effect and improving the resonator stability of diode-pumped anisotropy crystal lasers.     

Transient grating measurements of refractive-index changes in intensively pumped Yb-doped laser crystals

Mechanisms of transient light-induced refractive-index changes in Yb-doped crystals Yb:KYW, Yb:KGW and Yb:YVO₄ were studied. Relative amplitudes and lifetimes of the electronic component of phase gratings caused by the polarizability difference of the excited and unexcited Yb³⁺ ions and the thermal component arising from thermalization of the pump energy were measured. Polarizability difference values of the ground ² F _7/2 and the excited metastable ² F _5/2 levels at the testing wavelength of 633 nm were determined for all crystals. The thermal diffusivity of the samples was estimated for selected directions of the thermal gradient. An athermal direction, along which the thermal component of refraction disappears, was found in Yb:KYW crystal under specific experimental conditions. PACS 42.70.Hj; 42.65.An; 66.30.Xj