高损伤阈值可饱和吸收体锁模脉冲光纤激光器的研究进展

光纤激光器作为推动各领域发展的基础硬件,在轨道交通、光纤通信、新材料制造、动力电池加工、军事国防和医疗等领域都有广泛的应用价值.光纤激光器被动锁模技术的核心器件是可饱和吸收体,它对光纤激光器实现高能量、窄脉宽、大功率的激光输出起决定性作用.依托传统材料和传统结构的可饱和吸收体,由于无散热机制,光作用到材料上的光斑大小与光纤出射直径几乎相同,容易超过可饱和吸收体的损伤阈值从而造成损坏.因此,调整可饱和吸收体制备工艺和结构,对于提高可饱和吸收体的损伤阈值,实现性能优良、稳定性高的脉冲激光具有重要意义.本文综述了高损伤阈值可饱和吸收体国内外研究现状,指出了高损伤阈值可饱和吸收体可能的发展方向.     

Metal-Element-Incorporation Induced Superconducting Hydrogen Clathrate Structure at High Pressure

The recent observation of high critical temperature T_c in lanthanum and Yttrium hydrides confirms the key role of hydrogen cage(H-cage)in determining high superconductivity.Here,we present a new class of metastable H₁₂ clathrate structures based on the icosahedral cI 24-Na that can be stabilized by incorporation of metal elements.Analysis shows that the charge transfer from metal atoms to H atoms contributes to forming the H₁₂ clathrate.Nine dynamically stable structures are identified to exhibit superconductivity,and a maximum T_c of 28K is found in voids-doped Mo₆H₂₄.Calculations reveal that the low T_c is attributed to the weak interaction between H atoms in each cage due to the long H–H distance.The current results provide a possible route to design H-cage containing superconductors.     

湖北典型地区茶叶-土壤重金属相关性研究

本文旨在分析湖北典型地区茶叶以及土壤中各种元素的含量,采用原子荧光法(AFS)和电感耦合等离子体质谱法(ICP-MS)等方法对135对茶叶及土壤样品进行测定,并探讨各种元素之间的相互关系和影响。研究结果表明,土壤中元素的分布对茶叶中元素含量分布有一定意义,典型区土壤养分有效磷和碱解氮较丰富,有机质和速效钾较缺乏。典型区茶叶作物表层土壤 Cd、Pb、Cu、Cr、As 均存在不同程度的超标。土壤 Cd 和 Hg 的污染指数高,潜在生态风险强。典型区茶叶可食部分重金属含量均值依次为 Cu>Pb>Cd>Hg>As>Cr,重金属元素在茶叶中含量均为中等变异性。 茶叶对 Cu、Pb 的富集系数明显高于 Hg、As、Cd、Cr,不同茶叶对同一元素的富集能力存在差异。土壤重金属含量与土壤 pH 值、CEC、有效磷、总氮等理化指标关系密切。茶叶重金属含量与土壤重金属含量水平相关性较弱,但与茶叶对重金属的富集能力均呈显著正相关关系。     

Femtosecond Fiber Laser Based on BiSbTeSe2 Quaternary Material Saturable Absorber

Topological insulator materials, including Bi₂Te₃, Sb₂Te₃, Sb₂Te₃, and Bi₂Se₃, have attracted some attention due to their narrow band gaps, high carrier mobility, wide spectral absorption ranges and other characteristics.We report a new multi-compound topological insulator material BiSbTeSe₂ that, compared with the traditional topological insulator composed of two elements, can integrate the physic...     

Tunable Dual-Wavelength Fiber Laser in a Novel High Entropy van der Waals Material

Fiber lasers with different net dispersion cavity values can produce some types of solitons, and rich nonlinear dynamics phenomena can be achieved by selecting different saturable absorbers. A new layered high-entropy van der Waals material(HEX)(Mn,Fe,Co,Ni)PS₃ was selected as a saturable absorber to achieve a high-power laser output of 34 m W. In addition, the wavelength can be dynamically tuned from 1560 nm to 1531 nm with significant dual-wavelength phenomena at 460 fs pulse durati...