Nd:GGG激光晶体的同步辐射X射线白光形貌研究

应用同步辐射X射线白光形貌术,对Nd:GGG晶体中的缺陷进行了研究,观察到晶体中的主要缺陷是生长条纹和位错,对生长条纹产生的机理和位错的类型进行了分析讨论,生长条纹是由于温度波动引起生长率的起伏产生的,确定晶体中的位错有刃型位错、螺旋位错和混合位错.根据生长条纹和位错的生成机制,提出了一些改进生长工艺的措施和方法,为生长质量更高的晶体提供了参考.     

Nd∶GGG激光晶体的同步辐射X射线白光形貌研究

应用同步辐射X射线白光形貌术,对Nd∶GGG晶体中的缺陷进行了研究,观察到晶体中的主要缺陷是生长条纹和位错,对生长条纹产生的机理和位错的类型进行了分析讨论,生长条纹是由于温度波动引起生长率的起伏产生的,确定晶体中的位错有刃型位错、螺旋位错和混合位错。根据生长条纹和位错的生成机制,提出了一些改进生长工艺的措施和方法,为生长质量更高的晶体提供了参考。     

高质量自调Q激光晶体Cr4+,Nd3+:Gd3Ga5O12的生长

用固相合成、共沉淀等方法合成了Cr4+,Nd3+GGG晶体的单相多晶材料.讨论了共沉淀法和固相合成法合成GGG单相的技术参数.用合成的单相多晶原料生长了高质量的Cr4+,Nd3+GGG单晶.通过测晶体的光谱性质发现Cr4+,Nd3+GGG晶体在400nm和520nm附近存在Cr3+离子的强的吸收峰.在808nm附近存在Nd3+离子宽的吸收带,能与InGa二极管激光有效的耦合;在1100附近有Cr4+的较强的吸收带,可实现对Nd3+的自调Q输出.Cr4+,Nd3+GGG晶体的荧光光谱与NdGGG晶体的一样,发光中心也位于1062nm,但其强度约为NdGGG的1/5～1/6.Cr4+,Nd3+GGG晶体是一种非常有潜力的自调Q激光晶体,可以实现大功率激光器的小型化和全固化.     

193 nm激光下不同含量Y杂质CaF2晶体辐照损伤研究(英文)

氟化钙晶体的抗辐照性能是其在深紫外光刻应用中的关键性能之一,目前氟化钙晶体在193nm激光辐照下的损伤过程尚不清楚。本文报道了193 nm激光辐照下氟化钙晶体的损伤行为及影响损伤的关键缺陷因素。通过193nm激光辐照试验,发现晶体损伤主要表现为晶体内部产生的辐照诱导色心与表面产生的辐照诱导损伤坑。通过紫外–可见分光光度计对辐照诱导色心分析,并将不同色心吸收系数与Y杂质含量进行线性拟合。结果表明:Y离子具有与F心结构波函数发生重叠的低位轨道,两者发生轨道杂化易形成色心稳定结构;线性拟合结果表明Y离子含量与氟化钙晶体本征色心之间存在线性关系,说明Y元素是影响色心形成的关键杂质离子。实验表征了辐照诱导损伤坑的元素分布和结构缺陷。EDS结果表明损伤坑处伴随着钙元素含量上升和氟元素含量下降,证实H心扩散、F心聚集导致了辐照损伤;EBSD结果表明表面辐照损伤优先在位错处产生。因此,降低杂质含量及位错密度是提高氟化钙晶体在193 nm激光下抗辐照损伤性能的重要途径。     

KTiOAsO4晶体的生长缺陷研究

研究ＫＴｉＯＡｓＯ４的生长缺陷,对于改善它的性质和应用前景有很大的意义,本文利用化学腐蚀光学显微术和同步辐射Ｘ射线形貌术研究了ＫＴｉＯＡｓ析缺陷,实验结果表明,两种腐蚀剂对ＫＴＡ晶体的表面缺陷效果显著,ＫＴＡ晶体中主要的缺陷有铁电畴生产层,形界,位错和包裹物,了这些缺陷形成的原因。     

非完整形态KH2PO4晶体薄表面层生长特性

实时观察了非完整形态的KH_2PO_4(KDP)晶体在过饱和溶液中以薄表面层生长形式恢复其结晶学形态的过程。提出了晶体形态恢复的"最小多面体原理",即:在自由生长系统中,对于非完整形态的KDP晶体,当其以薄表面层形式恢复其结晶学完整形态时,薄表面层将选择相应的奇异面方向生长,使晶体形态最终恢复为一个由各结晶学显露面所围成的体积最小的凸多面体。利用PBC理论分析了生长基元在非结晶学显露面上的附着情况并阐述了锥顶处薄表面层倒垂生长的原因。结果表明,薄表面层形成与晶体非完整结晶学形态及不均匀水动力学条件相关联。柱面凹角与非正常棱边及Z切片正常棱角均可诱发产生薄表面层,且薄表面层生长终止于其所在奇异面的正常结晶学晶棱。     

Nd:GdxY1-xCa4O(BO3)3晶体的生长及其光谱性能研究

利用熔体提拉法生长了大尺寸,高质量的新型激光自倍频晶体Nd:GdxY1-x(Ca4O(BO3)3(简称Nd:GdYCOB),对Nd:GdYCOB晶体的XRD衍射图进行指标化,得到它的晶胞参数为a=8.080A;b=16.016A;c=3.538A,β＝101．18,μ＝491．1A3,对取自不同部位的晶体粉末进行ICP原子发射光 分析表明晶体整体组份均匀一致,根据熔体和晶体粉末的ICP数据计算,Nd:GdYCOB晶体中Nd3 的分凝系数为0．63,首次报道了Nd:GdYCOB晶体200－3000nm室温透过光谱和室温荧光光谱及荧光寿命,室温透过光谱表明Nd:GdYCOB晶体的紫外吸收边在－220nm,具有很宽的透光波段（－220－2700nm);Nd:GdYCOB晶体在800nm附近存在很强的吸收,适合于LD泵汪,为光光谱表明Nd:GdYCOB晶体是一种很有潜力的RGB（red,green,blue)激光自倍频晶体,掺杂4％,5％ Nd:GdYCOB晶体的荧光寿命分别为105us和100us。     

Nd:NaBi(WO4)2晶体光谱性能研究

采用提拉法生长出了四方晶系白钨矿结构的掺钕钨酸铋钠[分子式Nd:NaBi(WO4)2,简称Nd:NBW]晶体.通过TG-DTA分析得到晶体的熔点为936.2℃,从XRD分析得到晶胞参数a=b=0.5275nm,c=1.1493nm.测试了该晶体的红外光谱和拉曼光谱,讨论了晶体的振动归属.由吸收光谱可以看出,该晶体在802nm有较强的吸收峰,半峰宽约16nm,并计算了晶体中Nd3 的吸收截面积.     

近化学计量比In:Fe:LiNbO3晶体光学性能的研究

采用助溶剂法以TSSG技术生长近化学计量比SInFeLiNbO3晶体.测试S InFeLiNbO3晶体的晶格常数,SInFeLiNbO3晶体的晶格常数既小于LiNbO3晶体也小于InFeLiNbO3晶体.晶格常数的变化是由于Li+取代反位铌NbLi4+和占据锂空位引起的.测试SInFeLiNbO3晶体的红外光谱,OH-吸收峰移到3503.cm-1,测试SInFeLiNbO3晶体的指数增益系数Γ,SInFeLiNbO3晶体的Γ值达到28cm-1,高于InFeLiNbO3晶体.     

YVO4／Nd：YVO4复合晶体的制备及特性研究

采用先光胶再热处理的办法成功的键合了Nd：YVO4和YVO4复合晶体,改善了径向热分布不均匀的现象,并对复合晶体的相关特性进行了实验研究。当抽运光功率为17．85W时,Nd：YVO4单一晶体获得了7．69W的1．06um激光输出,光-光转换效率为43．1％;Nd：YVO4／YVO4复合晶体获得了9．25W的1．06um激光输出,光-光转换效率达到52％。     

Effect of Calcium on Nd:GdVO4 single crystal

The Ca_0.08Gd_0.92VO₄ crystal and Nd-doped Ca_0.08Gd_0.92VO₄ crystals were grown by the Czochralski method; the lattice parameters of the crystals were determined by XRD. The results showed that substituting Nd³⁺ caused an increase in lattice parameter; the segregation coefficient of Nd³⁺ ions in the crystal is lower than that of Nd:GdVO₄ crystal; the absorption spectra, fluorescence spectra, absorption cross-section and the emission cross-section of the Nd:Ca_0.08Gd_0.92VO₄ crystal were investigated at room temperature; furthermore, the Raman performance of Ca_0.08Gd_0.92VO₄ crystal was improved.     

Crystal quality and optical properties for Nd:GdVO4 single crystals by a floating zone method

Single crystals of neodymium-doped gadolinium orthovanadate (Nd:GdVO₄) were successfully grown by the floating zone method (FZ) with an infrared convergence type heater. These crystal quality and optical properties are sufficient for application to a laser host. Distribution of (Nd/Nd + Gd) concentration by 50 mm in the growth direction was 0.20 ± 0.02 against a target concentration of 0.20. Distribution of extinction ratio at 633 nm by 50 mm in the growth direction was 51 ± 2 dB. Laser performance for these crystals with a-cut were measured. The maximum slope efficiency was 65% and the maximum output power was 3.4 W with continuous wave at 808 nm.     

Low threshold, diode end-pumped Nd:GdVO4 self-Raman laser

Low threshold, high efficient Raman laser output has been realized from a compact, diode end-pumped, self-stimulating Nd³⁺:GdVO₄ Raman laser. Maximum Raman output power of 100 mW was achieved at a pulse repetition frequency (PRF) of 10 kHz with 1.8 W pump power. The optical efficiency is 5.6% from diode to Raman laser and the slope efficiency is 8%. The lowest threshold for the SRS process is only 400 mW at a PRF of 5 kHz. By generating second harmonics using a LBO crystal, 3 mW 588 nm yellow laser was also produced. A strong blue emission was observed in the Nd³⁺:GdVO₄ crystal when the Raman laser output, we contribute this for the upconversion of the Nd³⁺ in the crystal.     

Hydrothermally-induced morphological transformation of GdVO4:Eu

The aim of the present study is to investigate the effect of a wide pH range on morphology and luminescence properties of europium-doped gadolinium vanadate (GdVO₄:Eu³⁺). GdVO₄:Eu³⁺ powders were hydrothermally synthesized at 180 °C for 24 h in a wide pH range. The as-synthesized powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. The XRD results showed that GdVO₄:Eu³⁺ with the tetragonal structure formed at pH < 13 as a single phase and Gd(OH)₃ formed at pH ≥ 13 as a secondary phase. The SEM and TEM observations demonstrated the hydrothermally-induced morphological transformation of GdVO₄:Eu³⁺ powders by altering the pH of the synthesis solution. The possible mechanism for the morphological transformation was proposed. The intensities of the prominent peaks at 618 nm in the PL emission spectra of GdVO₄:Eu³⁺ powders considerably shift according to the specific morphology. The luminescence intensity of the octahedron- and rod-like GdVO₄:Eu³⁺ powders hydrothermally obtained at pH = 3 was the strongest one due to high packing density and high crystallinity as well as the extended reduction of the concentration of inherent defect states or adsorbed species.     

Nonlinear optical properties of BaWO4 crystal

Nonlinear refraction and nonlinear absorption in barium tungstate crystal which is widely used in Raman lasers is studied using the single-beam z-scan technique with 1 ps laser pulses at 790 and 395 nm. The nonlinear refraction-index intensity-coefficients at these wavelengths and two-photon absorption coefficient at 395 nm have been determined for the crystal. The results show that barium tungstate is characterized by weaker nonlinear refraction and absorption at 395 nm in comparison with other Raman crystals.     

Optical properties of Nd:NaLa (WO4)2 single crystal

Nd³⁺-doped NaLa(WO₄)₂ single crystal with a dimension of 20 mm × 40 mm and a good optical quality was grown by Czochralski method. The polarized absorption spectra and emission spectra were measured at room temperature. The absorption cross-section and emission cross-section were presented. The Judd–Ofelt theory, extended to anisotropic system, has been applied to evaluate the intensity parameters Ω_t (t = 2, 4, 6), radiative transition rates A, radiative lifetimes τ_R and fluorescent branching ratios β. The calculated radiative lifetime was compared with the experiment data for the ⁴F_3/2 emitting level. All spectral features are strongly affected by an inhomogeneous broadening connected with the ‘disordered crystal’ character of the title compound.     

Radiation damage study of MeV ions-implanted Nd:YVO4 crystal

Damage formation mechanism of Nd:YVO₄ implanted with MeV ions is investigated. MeV Si⁺ ions were implanted into Nd:YVO₄ crystal, and the lattice damage was measured using Rutherford backscattering spectroscopy/channeling (RBS/C) method. The damage creation kinetic indicates a significant contribution from electronic energy loss to the surface damage. A detailed analysis allows us to deduce the different contributions from electronic and nuclear stopping powers to the lattice damage production. An obvious difference in extent of damage from 1 MeV and 3 MeV Si⁺ implantations also implies that there exists a threshold value of the electronic energy deposition for damage formation. The exact value of threshold is obtained by comparison with the experimental data obtained from 3 MeV O⁺, F⁺ and Si⁺ implantation results, which turns out to be (1.7 ± 0.1) keV/nm.     

Concentration effect of Nd ion on the spectroscopic properties of Er/Nd co-doped LiYF4 single crystal

High quality Er³⁺/Nd³⁺:LiYF₄ single crystals were grown by a Bridgman method. Their spectroscopic properties were studied to understand the Nd³⁺ concentration effect upon excitation of an 800 nm laser diode. The intensest 2.7 μm emission was observed in the LiYF₄ crystal codoped with 0.99 mol% Er³⁺ and 0.62 mol% Nd³⁺. Meanwhile, the emission intensity for the green up-conversion and 1.5 μm downconversion of Er³⁺ decreased with increasing of the Nd³⁺ concentration. The modified Inokuti–Hirayama model was used to analyze the decay curves of the 1.06 (Nd³⁺) and 1.5 (Er³⁺) μm emissions. The results indicated that the energy transfer process (Er³⁺:⁴I_13/2 + Nd³⁺:⁴I_9/2 → Er³⁺:⁴I_15/2 + Nd³⁺:⁴I_15/2) is mainly due to the electric dipole–dipole interaction. The energy transfer efficiencies between Nd³⁺ and Er³⁺ ions were calculated. All results suggested that the Er³⁺/Nd³⁺:LiYF₄ single crystals may have potential applications in mid-infrared lasers.     

Nonlinear optical properties of the flux grown RbTiOPO4 crystal

Refractive indices of flux grown RbTiOPO₄ (RTP) were measured in the wavelength interval 0.406 to 1.064 μm and Sellmeier equation coefficients were calculated. Phase-matching curves for second harmonic generation from radiation with wavelengths of 1.064 μm and 1.079 μm were obtained. RTP nonlinear optical properties are compared to those of KTP. Second-harmonic generation in RTP crystal is carried out with the efficiency of 65%.     

Nd optical multisites in the Ca3(Nb,Ga)2Ga3O12 laser garnet crystal

Laser excited site-selective luminescence of Nd³⁺ ion in the Ca₃(Nb,Ga)₂Ga₃O₁₂ garnet crystal has been investigated for the and transitions. Six main non-equivalent crystal field sites were detected in the garnet. The crystal splitting scheme of the and manifolds was obtained for each Nd³⁺ site. Energy transfer between Nd³⁺ sites was observed by using time resolved spectroscopy.