Spectroscopic characterization of Yb:Sc_2O_3 transparent ceramics

Yb：Sc2O3 transparent ceramics are fabricated by a conventional ceramic process and sintering in H2 atmosphere. The room-temperature spectroscopic properties are investigated, and the Raman spectrum shows an obvious vibration characteristic band centred at 415 cm-1. There are three broad absorption bands around 891, 937, and 971 nm, respectively. The strongest emission peak is centred at 1.04 μm with a broad bandwidth （11 nm） and an emission cross-section of 1.8×10^-20 cm^2. The gain coefficient implies a possible laser ability in a range from 990 nm to 1425 nm. The energy-level structure shows that Yb：Sc2O3 ceramics have large Stark splitting at the ground state level due to their strong crystal field. All the results show that Yb：Sc2O3 transparent ceramics are a promising material for short pulse lasers.

Spectral and laser properties of Yb and Ho co-doped(YLa)_2O_3 transparent ceramic

Highly transparent Yb,Ho doped（YLa）2O3 ceramic was fabricated by conventional ceramic processing with nanopowders.The absorption and emission spectra of the ceramic was investigated.The energy transfer mechanism between Yb3＋ and Ho3＋ was also discussed.The strong emission band around 2 μm indicated that the Yb-Ho：（Y 0.90 La 0.10）2O3 transparent ceramic is a promising gain medium for the generation of 2 μm laser emissions.The laser operation of Yb-Ho co-doped（YLa）2O3 ceramic at 2.1 μm is first reported.

Synthesis and properties of Yb:Sc_2O_3 transparent ceramics

Yb：Sc2O3 transparent ceramics were fabricated by solid-state reaction and vacuum sintering method. CaO was added as sintering aids by a high energy ball milling. Transparent nearly-fully dense samples were obtained after 1840℃ sintefing. Using transmitted-light microscope we get the grain sizes are more than 100μm. Using spectrophotometer we get the absorption coefficient centered at 975 nm was 2.65 cm-1. The phosphorescence spectra showed that the line-widths （FWHM） at 975 and 1041 nm were about 4 and 10 nm and the lifetime of Yb ions in Sc2O3 transparent ceramics was about 883 μs. According to the absorption and fluorescence band centers of Yb：Sc2O3 transparent ceramics, the level scheme of Yb3＋ ions in Sc2O3 ceramics could be gotten.

Yb∶CaF_(2)透明陶瓷的压力辅助烧结及其性能研究

本文采用化学共沉淀法合成了5%(原子数分数,下同)Yb∶CaF_(2)纳米粉体。经过冷冻干燥后,粉体的团聚程度有所减轻,粉体呈立方片层状,平均颗粒尺寸约为40 nm。以冷冻干燥后的粉体为原料,通过热压烧结结合热等静压(HIP)烧结后处理制备了高光学质量的5%Yb∶CaF_(2)透明陶瓷。分析了热压烧结过程中样品的致密化行为,并对陶瓷的显微结构、直线透过率、吸收光谱及激光性能进行测试与表征。结果表明,陶瓷坯体在热压烧结时的保温阶段存在致密化驱动力的激活阈值,同时HIP后处理能够进一步压缩和排除热压陶瓷内残留气孔,有效提高陶瓷的光学质量。通过热压烧结(625℃×2 h,50 MPa)结合HIP后处理(600℃×3 h,100 MPa Ar)制备的5%Yb∶CaF_(2)透明陶瓷在400和1200 nm处的直线透过率分别为72.6%和92.2%(厚度2 mm),其在976 nm处的吸收截面为0.52×10^(-20)cm^(2)。使用波长为930 nm的光纤耦合二极管激光器(LD)端面泵浦Yb∶CaF_(2)透明陶瓷,获得了最大输出功率为0.81 W、斜率效率为9.7%的准连续激光输出。

Fabrication,microstructures,and optical properties of Yb:Lu_(2)O_(3) laser ceramics from co-precipitated nano-powders

The Yb:Lu_(2)O_(3)precursor made up of spherical particles was synthesized through the co-precipitation method in the water/ethanol solvent.The 5 at% Yb:Lu_(2)O_(3)powder is in the cubic phase after calcination at 1100℃ for 4 h.The powder also consists of spherical nanoparticles with the average particle and grain sizes of 96 and 49 nm,respectively.The average grain size of the pre-sintered ceramic sample is 526 nm and that of the sample by hot isostatic pressing grows to 612 nm.The 1.0 mm-thick sample has an in-line transmittance of 81.6%(theoretical value of 82.2%)at 1100 nm.The largest absorption cross-section at 976 nm is 0.96×1^(0-20)cm^(2) with the emission cross-section at 1033 nm of 0.92×10^(-20)cm^(2) and the gain cross sections are calculated with the smallest population inversion parameter β of 0.059.The highest slope efficiency of 68.7% with the optical efficiency of 65.1% is obtained at 1033.3 nm in quasi-continuous wave(QCW)pumping.In the case of continuous wave(CW)pumping,the highest slope efficiency is 61.0% with the optical efficiency of 54.1%.The obtained laser performance indicates that Yb:Lu_(2)O_(3)ceramics have excellent resistance to thermal load stresses,which shows great potential in high-power solid-state laser applications.

Y^(3+)∶CaF_(2)透明陶瓷的制备及其显微结构研究

采用化学沉淀法合成Y^(3+)∶CaF_(2)粉体,用真空热压烧结技术制备透明陶瓷。通过XRD、SEM与TEM分析粉体特性,并研究Y^(3+)∶CaF_(2)透明陶瓷显微结构与透过率的关系。结果表明,Y^(3+)∶CaF_(2)粉体为立方萤石相晶体结构。随Y^(3+)掺杂量的增加,粉体的平均粒径尺寸逐渐减小,晶胞参数由5.4521增大到5.4655;在900℃下烧结3 h得到的5%Y^(3+)掺杂的CaF_(2)陶瓷透过率最高,样品在500和1500 nm处的透过率分别为73.1%和86.4%。改变Y^(3+)掺杂量与烧结温度均可调控陶瓷的显微结构。晶粒生长速率低,气孔不易排出,速率过高,气孔易被包裹在晶粒内部,两种情况均会降低陶瓷的透过率。本研究工作为制备高品质复合结构CaF_(2)透明陶瓷提供了参考。

Yb∶Lu_(2)O_(3)透明陶瓷的制备及激光性能研究

稀土离子掺杂的倍半氧化物陶瓷材料具有高热导率、低声子能量、高激光损伤阈值等优势,在固体激光领域具有巨大的应用潜力。本文采用化学共沉淀法合成了高纯度、低团聚Yb∶Lu_(2)O_(3)陶瓷粉体,在氧气气氛下预烧后,结合热等静压(HIP)烧结制备了具有高致密度、高透过率的5%(原子数分数)Yb∶Lu_(2)O_(3)透明陶瓷。陶瓷的平均晶粒尺寸小于1μm,在1100 nm波长处的透过率超过81%。在974 nm波长处吸收截面为~0.97×10^(-20)cm^(2),在1.08μm波长处的发射截面为~0.39×10^(-20)cm^(2)。采用976 nm半导体激光器泵浦Yb∶Lu_(2)O_(3)陶瓷,室温条件下实现了11.67 W的连续激光输出,对应的斜效率为55.3%,激光中心波长为1080.1 nm。