1 安徽师范大学物理与电子信息学院，安徽芜湖 241002
2 中国科学院合肥物质科学研究院，安徽合肥 230031
二氧化碳（carbon dioxide, CO2）浓度监测是实现碳达峰、碳中和的重要基础，非分散红外（non-dispersive infrared, NDIR）检测技术作为温室气体测量领域应用最为广泛的技术之一，如何有效抑制温度漂移、确保长期监测数据的稳定性和可靠性是研究重点。实验表明，光源光功率、气体吸收线强、滤光片中心波长等容易受到环境温度影响。文中提出一种红外气体检测的温度补偿方法，研制了用于大气二氧化碳浓度红外检测的分析仪。选取以 4.26.m为中心波长的 CO2气体吸收线；利用高低温试验箱，对分析仪进行温度补偿实验研究；配置标准 CO2气体浓度，对分析仪进行浓度标定实验研究。测量结果表明，红外 CO2气体分析仪浓度测量稳定，温度补偿显著，具有快速响应、应用范围广等优点。该红外 CO2气体分析仪为陆地生态系统碳收支监测等领域提供可靠数据支撑。
二氧化碳 非分散红外 温度补偿 浓度标定 carbon dioxide, non-dispersive infrared, temperatu
中国矿业大学材料与物理学院，江苏 徐州 221116
采用等离子喷涂-化学气相沉积法制备Bi2O3薄膜，并研究了沉积温度和热处理温度对于Bi2O3薄膜形貌和成分的影响。用场发射扫描电子显微镜、X射线衍射仪、高分辨率透射电子显微镜对该薄膜形貌和成分进行了表征，通过紫外-可见光漫反射光谱仪研究了不同热处理温度下α/β-Bi2O3禁带宽度的变化。结果表明：沉积温度和热处理温度影响Bi2O3薄膜的微观形貌，同时影响α和β两相的相比例，但沉积温度的影响显著大于热处理温度；随着热处理温度升高，β相转化为α相的比例越来越高，α-Bi2O3和β-Bi2O3的禁带宽度都有所增加；最后，通过对甲基橙和双酚A的降解证明了Bi2O3薄膜具有良好的光催化降解性能。
氧化铋 薄膜 等离子喷涂 化学气相沉积 光催化降解 bismuth trioxide film plasma spraying chemical vapor deposition photocatalytic degradation
1 吉林大学, 超硬材料国家重点实验室, 长春 130012
2 吉林大学, 计算方法与软件国际中心, 长春 130012
3 吉林大学, 未来科学国际合作联合实验室, 长春 130012
理论晶体结构预测可以在给定化学组分的条件下确定材料的晶体结构, 已成为材料科学研究的重要工具。然而, 该方法一直面临计算成本高的瓶颈问题。近年来, 新兴机器学习方法在传统科学计算上展现了广阔的应用前景, 逐渐被引入到晶体结构预测领域。本文主要讨论机器学习方法在理论晶体结构预测领域的最新研究进展, 分别从加速晶体结构的能量计算和势能面的探索两个方面介绍领域的最新成果, 并对未来研究可能的发展提出抛砖引玉的见解。
机器学习 晶体结构预测 机器学习势 生成模型 machine learning crystal structure prediction machine learning potential generative model
无锡职业技术学院 机械技术学院，江苏 无锡 214121
采用激光熔覆技术，在45钢表面制备了钴基熔覆层。通过金相显微镜（OM）、扫描电子显微镜（SEM）、X射线能谱仪（EDS）和摩擦磨损试验机，检测熔覆层的微观结构组织、熔池形貌及熔覆层的耐磨损性能。结果表明，熔覆层质量随着激光功率的增大呈现先提高后降低的变化，达到2 000 W时，熔覆层质量最优，熔池较为稳定，无气孔等缺陷。熔覆层的显微组织从粗大弥散的柱状晶，转变为细小均匀的等轴晶，最终又变为粗大的柱状晶。在磨擦磨损试验中，随着激光功率的增大，熔覆层的磨损机理从块状剥落到颗粒磨损，其中功率为2 000 W时，熔覆层的耐磨性最优，实时摩擦因数最为平稳，磨损率仅为1.3×10-4 mm3/(N·m)。
激光熔覆 激光功率 表面强化 摩擦磨损 微观组织形貌 laser cladding laser power surface strengthening friction and wear microstructure morphology
可调谐半导体激光吸收光谱(tunable diode laser absorption spectroscopy, TDLAS)技术广泛应用于大气环境监测、燃烧诊断等领域, 具有高灵敏度、高选择性、响应速度快、适应恶劣环境、可多组分实时在线监测等优点。文中以TDLAS技术在大气环境检测中的应用为例, 根据基于TDLAS技术检测气体的方式不同分为直接吸收光谱(direct absorption spectroscopy, DAS)、频率调制光谱(frequency modulation spectroscopy, FMS)和波长调制光谱(wavelength modulation spectroscopy, WMS)技术, 介绍了高灵敏调制光谱技术, 简要评述了TDLAS在大气环境检测领域的研究进展和发展趋势。
可调谐半导体激光吸收光谱 大气环境 气体检测 高灵敏调制光谱 tunable diode laser absorption spectroscopy (TDLAS atmospheric environment gas detection high sensitive modulation spectroscopy
Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
2 National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China, Beijing 100010, China
3 State Key Laboratory of High Performance Computing, College of Computer, National University of Defense Technology, Changsha 410073, China
4 Beijing Academy of Quantum Information Sciences, Beijing 100193, China
5 Science and Technology on Surface Physics and Chemistry Laboratory, Jiangyou 621908, China
Helicity-dependent ultrafast spin current generated by circularly polarized photons in topological materials holds the crux to many technological improvements, such as quantum communications, on-chip communication processing and storage. Here, we present the manipulation of helicity-dependent terahertz emission generated in a nodal line semimetal candidate Mg3Bi2 by using photon polarization states. The terahertz emission is mainly ascribed to the helicity-dependent photocurrent that is originated from circular photogalvanic effects, and the helicity-independent photocurrent that is attributed to linear photogalvanic effect. Our work will inspire more explorations into novel nodal line semimetals and open up new opportunities for developing ultrafast optoelectronics in the topological system.
terahertz spin photocurrent nodal-line semimetal topological material Opto-Electronic Advances
2020, 3(12): 12200023
兴义民族师范学院生物与化学学院, 贵州省化学合成及环境污染控制和修复技术特色重点实验室, 兴义 562400
以二水氯化铜(CuCl2?2H2O)、硅酸钠(Na2SiO3)、钼酸钠 (Na2MoO4) 和2,6-二甲基-3,5-二(吡唑-3-基)吡啶(简写为H2L)为原料, 通过水热反应, 成功地合成了一个一维链状Keggin型多酸基杂化化合物[Cu2(H3L)2](SiMo12O40)。通过X-射线单晶衍射、TGA、 IR以及元素分析对该化合物的结构进行表征。测试 结果表明, 该化合物属于三斜晶系, P-1空间群, 晶胞参数a=1.168 9(5) nm,b=1.215 7(5) nm, c=1.223 3(5) nm, α=62.066(5)°, β=62.833(5)°, γ=74.789(5)°, V=1.363 8(10) nm3, Z=2, R1=0.082 4, wR2=0.174 5。电化学分析结果表明该化合物对亚硝酸盐的还原具有良好的电催化效果。
多酸 水热合成 晶体结构 电化学 一维 polyoxometalate hydrothermal synthesis crystal structure electrochemistry one-dimension
Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
2 State Key Laboratory of High Performance Computing, National University of Defense Technology, Changsha 410073, China
3 National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China, Beijing 100010, China
4 State Key Laboratory of Laser Interaction with Matter, Northwest Institute of Nuclear Technology, Xi’an 710024, China
Standing on the potential for high-speed modulation and switching in the terahertz (THz) regime, all-optical approaches whose response speeds mainly depend on the lifetime of nonequilibrium free carriers have attracted a tremendous attention. Here, we establish a novel bi-direction THz modulation experiment controlled by femtosecond laser for new functional devices. Specifically, time-resolved transmission measurements are conducted on a series of thin layers Bi2Se3 films fabricated straightforwardly on Al2O3 substrates, with the pump fluence range from 25 μJ/cm2 to 200 μJ/cm2 per pulse. After photoexcitation, an ultrafast switching of THz wave with a full recovery time of ~10 ps is observed. For a longer timescale, a photoinduced increase in the transmitted THz amplitude is found in the 8 and 10 quintuple layers (QL) Bi2Se3, which shows a thickness-dependent topological phase transition. Additionally, the broadband modulation effect of the 8 QL Bi2Se3 film is presented at the time delays of 2.2 ps and 12.5 ps which have a maximum modulation depth of 6.4% and 1.3% under the pump fluence of 200 μJ/cm2, respectively. Furthermore, the absorption of α optical phonon at 1.9 THz shows a time-dependent evolution which is consistent with the cooling of lattice temperature.
Ultrafast optics topological insulator ultrafast photonic devices Photonic Sensors
2019, 9(3): 268
Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
2 National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China, Beijing 100071, China
3 State Key Laboratory of High Performance Computing, College of Computer, National University of Defense Technology, Changsha 410073, China
In this work, a soliton mode-locked erbium-doped fiber laser (EDFL) with a high-quality molecular beam epitaxy (MBE)-grown topological insulator (TI) Bi2Se3 saturable absorber (SA) is reported. To fabricate the SA device, a 16-layer Bi2Se3 film was grown successfully on a 100 μm thick SiO2 substrate and sandwiched directly between two fiber ferrules. The TI-SA had a saturable absorption of 1.12% and a saturable influence of 160 MW/cm2. After inserting the TI-SA into the unidirectional ring-cavity EDFL, self-starting mode-locked soliton pulse trains were obtained at a fundamental repetition rate of 19.352 MHz. The output central wavelength, pulse energy, pulse duration, and signal to noise ratio of the radio frequency spectrum were 1530 nm,18.5 pJ, 1.08 ps, and 60 dBm, respectively. These results demonstrate that the MBE technique could provide a controllable and repeatable method for the fabrication of identical high-quality TI-SAs, which is critically important for ultra-fast pulse generation.
140.4050 Mode-locked lasers 160.4236 Nanomaterials Chinese Optics Letters
2019, 17(7): 071403
Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
2 State Key Laboratory of High Performance Computing, College of Computer, National University of Defense Technology, Changsha 410073, China
3 Interdisciplinary Center of Quantum Information, National University of Defense Technology, Changsha 410073, China
4 National Institute of Defense Technology Innovation, Academy of Military Sciences PLA China, Beijing 100010, China
Broadband transient reflectivity traces were measured for Bi2Se3 thin films with various substrates via a 400 nm pump–white-light-probe setup. We have verified the existence of a second Dirac surface state in Bi2Se3 and qualitatively located it by properly analyzing the traces acquired at different probe wavelengths. Referring to the band structure of Bi2Se3, the relaxation mechanisms for photo-excited electrons with different energies are also revealed and studied. Our results show a second rise of the transient reflection signal at the time scale of several picoseconds. The types of substrate can also significantly affect the dynamics of the rising signal. This phenomenon is attributed to the effect of lattice heating and coherent phonon processes. The mechanism study in this work will benefit the fabrication of high-performance photonic devices based on topological insulators.
160.4236 Nanomaterials 300.6500 Spectroscopy, time-resolved Chinese Optics Letters
2019, 17(2): 020005
