Ho:YV0(4) solid-state saturable-absorber Q switch for a 2-µm Tm, Cr:Y(3)Al(5)O(12) laser

The holmium-doped yttrium orthovanadate (Ho:YVO(4)) crystal was shown to be an effective solid-state saturable-absorber Q switch for a flash-lamp-pumped Tm,Cr:Y(3)Al(5)O(12) laser operating at 2.017 μm. A single Q-switched laser pulse of 3.5 mJ in energy and 45 ns in duration was observed with a 1-mm-thick 4% Ho:YVO(4) solid-state saturable absorber, which was grown with the high-temperature-solution-growth method.     

Room-temperature 1.643-µm Er(3+):Y(3)Sc(2)Ga(3)O(12) (Er:YSGG) laser

Laser operation at 1.643 μm ((4)I(13/2)-(4)I(15/2)) in Er(3+):Y(3)Sc(2)Ga(3)O(12) (Er:YSGG) at 300 K is reported. An Er:glass laser (1.532 μm) was used in an end-pumping arrangement to obtain laser output from a 1-cm-long 0.7% Er(3% Yb, 1% Cr):YSGG crystal in an external cavity. The Er:YSGG laser exhibited an 18-mJ threshold and a 10% slope efficiency.     

Diode-pumped 2 μm vibronic (Tm3+, Yb3+):KLu(WO4)2 laser

We report on laser operation in a (6 at. % Tm, 5 at. % Yb):KLu(WO4)2 codoped crystal. The vibrational frequencies of KLu(WO4)2 are coupled to the electronic transitions of Tm3+ at 1946 nm, creating virtual final laser levels at higher energy than the ground level 3H6 of Tm3+. The longest recorded laser wavelength was 2039 nm, which is longer than permitted by a pure electronic transition in Tm3+ ions in KLu(WO4)2. We show that every laser wavelength can be explained with the electron-phonon coupling effect, where the vibration frequencies were determined through Raman spectroscopy.     

(Y3-x-yREx)Al5O12:Cey(RE=Tb,Gd)荧光粉晶体结构与光致发光

采用化学共沉淀法合成具有Tb、Gd稀土掺杂的Y3Al5O12:Ce3 荧光粉,通过XRD和荧光光谱研究其晶体结构和光致发光.结果表明,(Y2.95-xTbx)Al5O12:Ce3 和(Y2.95-xGdx)Al5O12:Ce3 系列荧光粉具有与Y3Al5O12:Ce3 相同的石榴石晶体结构,但晶胞参数随Tb、Gd取代Y而略有增加;随Tb、Gd掺杂量增加,荧光粉发射波长逐渐红移,当x=2.95时,发射波长λmax分别从532nm红移至551和542nm;根据晶体场理论解释了荧光粉发射波长红移现象.这种发射波长红移的荧光粉能够显著地增强蓝光LED芯片与荧光粉组合形成的白光中红光成分,进而改善白光LED光源质量.     

激光区熔定向凝固Al2O3/Y3Al5O12 (YAG)共晶的组织与断裂韧性

采用激光区熔高温度梯度快速定向凝固技术从熔体中直接制备Al2O3/Y3Al5O12(YAG)共晶自生复合陶瓷,以研究其在超高温度梯度(1.0×106 K/m)下的快速凝固组织特征及与激光工艺参数的关系,并对其力学性质进行分析.研究结果表明:凝固组织强烈地受激光扫描速度与功率密度的影响,当二者匹配时,Al2O3相和Y3Al5O12(YAG)相呈现均匀一致,连续分布的层状耦合共晶结构,共晶间距细小(1～2 μm),且随扫描速度的增大逐渐减小;所制备的Al2O3/Y3Al5O12(YAG)共晶陶瓷硬度高达19.5 GPa,断裂韧性达到3.6 MPa·m1/2.     

(Cr,Tm,Ho):YAG晶体中Tm~(3+)离子的中介能量转移作用

测定了晶体的吸收谱，荧光谱和荧光寿命，用Taylor和Dexter理论计算了Cr3+－Ho3+,Cr3+－Tm3+和Tm3_－Ho3+离子间能量转移效率和转移几率．讨论了（Cr，Tm．Ho）：YAG晶体中Tm3+的能量转移中介作用．     

超重力辅助燃烧合成Y2O3-Al2O3-SiO2玻璃/Y3Al5O12陶瓷梯度复合材料

以超重力场辅助燃烧合成技术制备了呈梯度分布的Y2O3-Al2O3-SiO2透明玻璃/Y3Al5O12陶瓷梯度复合材料.结果表明,梯度布置两种组分的原料既可防止下层熔体的喷溅,又能提高上层玻璃的透过率.该梯度材料沿超重力方向依次为YAS透明玻璃层、YAS-YAG玻璃陶瓷层和YAG陶瓷层.     

Phase Relations in the Systems Al2TiO5–Fe2O3 , Al2O3–TiO2–Fe2O3 , and Al2TiO5–Cr2O3

Phase relations in the systems Al₂TiO₅–Fe₂O₃, Al₂TiO₅–Cr₂O₃, and Al₂O₃–TiO₂–Fe₂O₃ are investigated, and the composition ranges of pseudobrookite Al_{2 – 2x} M_2x TiO₅ (M = Fe, Cr) solid solutions are determined.     

High-efficiency 1.06-µm output in a monolithic Nd:YVO(4) laser

A miniature 1.5-mm-long monolithic Nd:YVO(4) laser was end pumped with a Ti-sapphire laser. The Nd-doping density was 3 at. %. The maximum output power obtained with 885 mW of absorbed pump power was 495 mW at 1.064 μm. The maximum slope efficiency was 57%, and the output power was only slightly dependent on pump polarization. Laser diode pumping was also demonstrated. Thermal effects were observed to reduce the output power and required active cooling of the laser crystal.     

钕离子掺杂钇铝石榴石(Nd3+:Y3Al5O12)透明陶瓷研究进展

回顾了新一代激光工作物质Nd3+:Y3Al5O12透明陶瓷的发展历史,并与激光晶体进行了比较,介绍了其技术优势,同时简述了Nd3+:Y3Al5O12透明陶瓷的2种常用工艺.     

Synthesis of (Fe,Cr)3Al–Al2O3 nanocomposite through mechanochemical combustion reaction induced by ball milling of Cr,Al and Fe2O3 powders

In this work, (Fe,Cr)₃Al matrix nanocomposite reinforced by 47 vol.% Al₂O₃ was synthesized by mechanochemical reaction of Cr, 3Al and Fe₂O₃ powders mixture. The structural evaluation of powder particles during milling was done by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and differential thermal analysis (DTA). The results showed that at the early stage of milling, the thermite reaction between Fe₂O₃ and Al occurred and Fe and Al₂O₃ phases were formed. Then, the remaining Al and Cr were alloyed with Fe, leading to (Fe,Cr)₃Al–Al₂O₃ nanocomposite structure. Further investigations indicated that the presence of diluents (excess Al and Cr) did not change the modality of thermite reaction and the formation of (Fe,Cr)₃Al–Al₂O₃ nanocomposite proceeded with combustion process. The (Fe,Cr)₃Al–Al₂O₃ nanocomposite powder exhibited the hardness value of 1140 Hv which is significantly higher than 935 Hv obtained for (Fe,Cr)₃Al.     

纳米(ZnO,Al2O3)复合掺杂对3Y2O3-ZrO2材料电性能的影响

以3Y2O3—ZrO2纳米粉和ZnO，A12O3纳米粉为原料，采用交流阻抗谱技术对掺少量ZnO和A12O3的3Y2O3—ZrO2烧结陶瓷进行电性能研究。研究表明：少量纳米ZnO掺杂降低了3Y2O3—ZrO2的电导率，但随着掺人量的增加，电导率开始回升。在ZnO掺杂样品中加入少量纳米A12O3进行复合第二相掺杂，结果提高了3Y2O3—ZrO2材料的电导率。同时少量A12O3的掺人降低了晶粒电导活化能，使得晶粒电导率增加。     

Dy3+:Y3Al5O12粉体的制备及发光性能研究

采用溶胶-凝胶/燃烧合成法制备了不同Dy3+掺量的Y3Al5O12发光体.分析了基质晶体结构、Dy3+掺量、Re3+的电荷半径比(Z/r)对Dy3+发光强度及发光颜色的影响.结果表明,Dy3+:Y3Al5O12样品的激发主峰位于353nm(6H15/2→6P7/2)附近;由于Dy3+所占据的Y3+位置具有D2对称性,具有一个反演对称中心,使得Dy3+的发射光谱以481nm蓝光发射为发射主峰,但黄蓝光发射强度之比(Y/B)随Dy3+离子浓度的变化很小.     

Processing and Properties of Al2O3-ZrO2(3Y)-SiC Nanocomposites

本文研究了非均相沉淀法制备 Al     

Efficient laser operation of diode-pumped Nd:KGd(WO4)2 crystal at 1.067 µm

The spectral properties and laser performance of a Nd:KGd(WO(4))(2) (Nd:KGW) rod pumped by a laser diode have been studied. The Nd:KGW can be doped with a much higher Nd3(+) concentration and has a wider absorption linewidth around 808 nm compared with Nd:YAG. At low repetition rates, the Nd:KGW exhibited good lasing properties with a lower threshold. The maximum optical-to-optical conversion efficiency of the diode laser pumped Nd:KGW laser at 1.067 μm has been determined to be 34.3% with a slope efficiency of 43.1%.     

低温反应溅射沉积α-(Al,Cr)_2O_3膜

使用AlCr合金靶材在高功率脉冲磁控溅射系统中低温反应溅射沉积氧化物薄膜,并与使用纯Al靶反应溅射的薄膜对比。用纳米压痕仪测量薄膜的力学性能,使用扫描电镜(SEM)、掠入射X射线衍射(GIXRD)和能谱仪(EDS)等手段研究了沉积薄膜的表面形貌、相结构和元素组成。结果表明,反应溅射Al时靶表面火花放电严重且工艺不稳定,因此所沉积的薄膜表面粗糙、疏松,硬度低;而反应共溅射AlCr能抑制靶表面火花放电,沉积薄膜平整、致密且硬度高;在540℃和10%氧分压条件下,可沉积出以α-(Al,Cr)_2O_3为主的刚玉型结构氧化物薄膜。     

高分散、均混合Al2O3-SiC-ZrO2(3Y)水悬浮液

用微波法制备纳米水合二氧化锆, 通过包覆工艺, 将Y(OH)3均匀地包覆在水合二氧化锆粒子表面, 制备出ZO2(3Y)的先驱体. 然后用聚甲基丙烯酸铵(PMAA-NH4)对α-Al2O3、纳米SiC及包覆水合二氧化锆表面改性. 使三种单相水悬浮液在pH=9.0时, 粒子表面电性相同, 且有良好分散状态. 从而制备出高分散、均混合Al2O3-SiC-ZrO2(3Y)先驱体水悬浮液.     

The role of fluorine in the devitrification of SiO2·Al2O3·P2O5·CaO·CaF2 glasses

A series of eight glasses based on a glass system with the generic composition 1.5(5–Z)SiO₂·(5–Z) Al₂O₃·1.5P₂O₅·(5–Z)CaO·ZCaF₂ were studied where Z = 2, 1.75, 1.5, 1.25, 1, 0.5, 0.25, 0. These glasses were characterised using differential scanning calorimetry (DSC) and x-ray powder diffraction (XRD). Glasses with high fluorine contents were found to crystallise readily to fluorapatite via a homogeneous nucleation route probably involving prior amorphous phase separation. These results are explained in terms of an approach which views glasses as being inorganic polymers where the presence of fluorine disrupts the glass network and thereby reduces the energy barrier to homogeneous nucleation and crystallisation of fluorapatite.     

Spectral properties of Ho3+/Tm3+ co-doped β′-Gd2(MoO4)3 crystal as laser gain medium around 2.0 μm

Ho³⁺/Tm³⁺ co-doped β′-Gd₂(MoO₄)₃ single crystal was investigated as gain medium for Ho³⁺ laser around 2.0 μm. Polarized absorption and fluorescence spectra of the crystal were measured. Polarized spectral parameters of Ho³⁺ ions in the crystal were calculated and the gain curves around 2.0 μm were estimated. The fluorescence decay curves for Tm³⁺ and Ho³⁺ ions related to the 2.0 μm laser were measured and analyzed. The distinct coupled decay behavior for the Ho³⁺/Tm³⁺ co-doped system embodies the existence of energy transfer between Tm³⁺ and Ho³⁺ ions.     

超重力下燃烧合成Al2O3-ZrO2(Y2O3)共晶陶瓷组织性能演化

采用超重力下燃烧合成工艺进行Al2O3-ZrO2 (4Y)共品陶瓷的制备,研究了Al2O3-ZrO2(4Y)共晶陶瓷的凝固行为、组织演化与力学性能的关系.XRD、SEM与EDS分析显示陶瓷基体组织是由表层的微纳米晶组织和心部的ZrO2四方相微米球品组织组成.陶瓷表层微纳米品组织的形成是因Al2O3高熵相率先形核和Al2O3各向异性生长,诱发Al2O3-ZrO2(4Y)小平面-小平面共晶生长所致;处于陶瓷心部的ZrO2四方相微米球晶组织则是因ZrO2高温立方相快速生长,导致Al2O3和ZrO2独立长大所致.力学性能测试结果表明因陶瓷凝固行为引起的显微组织演化,使其表层具有最大的维氏硬度(20.2GPa),而其心部则具有最高的断裂韧性(18.5±1.6MPa·m1/2),陶瓷弯曲强度达至1268±112MPa.