Author Affiliations
Abstract
1 Information Materials and Intelligent Sensing Laboratory of Anhui Province, Key Laboratory of Opto-Electronic Information Acquisition and Manipulation of Ministry of Education, School of Physics and Opto-electronics Engineering, Anhui University, Hefei 230601, China
2 School of Instrument Science and Opto-electronics Engineering, Laboratory of Optical Fibers and Micro-nano Photonics, Hefei University of Technology, Hefei 230009, China
3 School of Opto-electronic Engineering, Zaozhuang University, Zaozhuang 277160, China
Random lasers are a type of lasers that lack typical resonator structures, offering benefits such as easy integration, low cost, and low spatial coherence. These features make them popular for speckle-free imaging and random number generation. However, due to their high threshold and phase instability, the production of picosecond random lasers has still been a challenge. In this work, we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers. Notably, stable picosecond random laser emission lasting 600 ps is observed at a low pump energy of 50 µJ, indicating the gain-switching mechanism. Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level. When the intensity of the continuously pumped light reaches a specific value, the number of inversion populations in the “scattering cavity” surpasses the threshold rapidly. Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon. This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.
random laser polymer optical fiber gain-switched laser picosecond pulse Chinese Optics Letters
2024, 22(4): 040603
1 昆明物理研究所, 云南 昆明 650223
2 陆军装备部驻重庆地区军事代表局, 重庆 400000
3 空军装备部驻成都地区军事代表局, 四川 成都 610000
4 海军装备部驻广州地区军事代表局, 广东 广州 510320
长波红外变焦光学系统相对于中波红外变焦光学系统存在可用材料少、系统高低温环境无热化难度大等难题。本文采用机械补偿变焦技术实现光学多视场变焦，利用主动补偿的消热差技术使系统在−40 °C~+65 °C温度范围内能够清晰成像，实现四片透镜架构的制冷型长波红外四视场光学系统设计。该光学系统四视场焦距分别为25 mm、109 mm、275 mm、400 mm，变倍比为15，光学系统包络尺寸为268 mm（长）×200 mm（宽），光学零件总质量为618 g。该光学系统具有质量轻、性能高、成本低等SWaP-C特征，在辅助导航、搜索、跟踪等安防领域中具有较大应用潜力。
制冷型长波红外 变焦光学系统 机械补偿 无热化 cooled long-wave infrared zoom optic system mechanical compensation athermalization 
Author Affiliations
Abstract
HEDPS, CAPT, College of Engineering and School of Physics, Peking University, Beijing 100871, People’s Republic of China
In traditional finite-temperature Kohn–Sham density functional theory (KSDFT), the partial occupation of a large number of high-energy KS eigenstates restricts the use of first-principles molecular dynamics methods at extremely high temperatures. However, stochastic density functional theory (SDFT) can overcome this limitation. Recently, SDFT and the related mixed stochastic–deterministic density functional theory, based on a plane-wave basis set, have been implemented in the first-principles electronic structure software ABACUS [Q. Liu and M. Chen, Phys. Rev. B 106, 125132 (2022)]. In this study, we combine SDFT with the Born–Oppenheimer molecular dynamics method to investigate systems with temperatures ranging from a few tens of eV to 1000 eV. Importantly, we train machine-learning-based interatomic models using the SDFT data and employ these deep potential models to simulate large-scale systems with long trajectories. Subsequently, we compute and analyze the structural properties, dynamic properties, and transport coefficients of warm dense matter.
Matter and Radiation at Extremes
2024, 9(1): 015604
Author Affiliations
Abstract
1 Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang, China
2 Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing, China
All-fiber coherent beam combiners based on the self-imaging effect can achieve a near-perfect single laser beam, which can provide a promising way to overcome the power limitation of a single-fiber laser. One of the key points is combining efficiency, which is determined by various mismatches during fabrication. A theoretical model has been built, and the mismatch error is analyzed numerically for the first time. The mismatch errors have been numerically studied with the beam quality and combining efficiency being chosen as the evaluation criteria. The tolerance of each mismatch error for causing 1% loss is calculated to guide the design of the beam combiners. The simulation results are consistent with the experimental results, which show that the mismatch error of the square-core fiber is the main cause of the efficiency loss. The results can provide useful guidance for the fabrication of all-fiber coherent beam combiners.
all-fiber coherent beam combination mismatch analysis self-imaging High Power Laser Science and Engineering
2024, 12(2): 02000e13
1 北京市农林科学院信息技术研究中心， 北京 100097 辽宁科技大学土木工程学院， 辽宁 鞍山 114051
2 北京市农林科学院信息技术研究中心， 北京 100097 农业部农业遥感机理与定量遥感重点实验室， 北京 100097
3 辽宁科技大学土木工程学院， 辽宁 鞍山 114051
具有极高营养价值且被誉为东方“橄榄油”的油茶树是我国南方地区重要经济林， 我国是世界上油茶树分布最广的国家。 提取油茶种植分布和面积对林业部门开展油茶的宏观管理和生产指导具有重要意义。 以地处亚热带地物复杂且多山地丘陵的湖南省常宁市为研究区， 该区域分布有大量农田和森林， 且部分植被季节变化较大， 对油茶的遥感提取带来了很大挑战。 提出了基于春夏秋三期的GF-2号高分辨率卫星影像， 综合植被指数、 纹理特征、 PCA主成分3种特征， 以及春夏、 春秋、 夏秋、 春夏秋四种不同时序组合和随机森林（RF）算法共构建了17种分类场景（S1—S17）， 运用随机森林（RF）、 支持向量机（SVM）、 最大似然（MLC）三种不同分类算法开展油茶遥感提取实验， 筛选出最优特征组合、 最佳分类季节与最优时序组合、 最优分类方法。 结果表明: 仅基于光谱信息分类精度低， 纹理特征的加入可大幅提升精度， 而PCA对于精度的提升效果微弱; 通过比较不同季节单时期的分类结果发现油茶提取精度最高的季节为夏季， 夏季单时期影像在最优特征组合(S8)中油茶生产者精度（PA）为94.06%， 油茶用户精度（UA）为92.57%; 在分类场景S10—S17中实验发现， 采用时序信息要比单时期影像有明显的精度提升， 时序组合分类精度由高到低依次为: 春夏秋、 春夏、 春秋、 夏秋; 综合光谱、 纹理、 时序信息通过随机森林（RF）、 支持向量机（SVM）、 最大似然（MLC）进行油茶提取， 随机森林算法分类精度总体表现最好。 采用春夏秋多时相遥感植被指数、 纹理、 PCA的随机森林方法(S17)是分类精度最高的方案， 总体精度（OA）和Kappa系数分别为96.85%和0.961 0， 油茶生产者精度（PA）为98.31%， 油茶用户精度（UA）为94.33%; 采用春夏时相遥感植被指数、 纹理的随机森林方法（S10）为兼顾计算效率与精度的最优方案， 总体精度（OA）和Kappa系数分别为95.62%和0.9458， 油茶生产者精度（PA）为96.93%， 油茶用户精度（UA）为95.09%。 所提出的最佳油茶遥感提取方案能够为亚热带地区油茶及其他经济林的遥感监测提供参考。
油茶 遥感 时序 植被指数 纹理特征 Camellia oleifera Remote sensing Time sequence Vegetation index Texture features 光谱学与光谱分析
2023, 43(5): 1589
强激光与粒子束
2023, 35(12): 124009
Author Affiliations
Abstract
1 School of Materials Science and Engineering, Shanghai University, Shanghai 200444, People’s Republic of China
2 Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, People’s Republic of China
3 Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 81000, People’s Republic of China
Aqueous sodium-ion batteries have attracted extensive attention for large-scale energy storage applications, due to abundant sodium resources, low cost, intrinsic safety of aqueous electrolytes and eco-friendliness. The electrochemical performance of aqueous sodium-ion batteries is affected by the properties of electrode materials and electrolytes. Among various electrode materials, Mn-based electrode materials have attracted tremendous attention because of the abundance of Mn, low cost, nontoxicity, eco-friendliness and interesting electrochemical performance. Aqueous electrolytes having narrow electrochemical window also affect the electrochemical performance of Mn-based electrode materials. In this review, we introduce systematically Mn-based electrode materials for aqueous sodium-ion batteries from cathode and anode materials and offer a comprehensive overview about their recent development. These Mn-based materials include oxides, Prussian blue analogues and polyanion compounds. We summarize and discuss the composition, crystal structure, morphology and electrochemical properties of Mn-based electrode materials. The improvement methods based on electrolyte optimization, element doping or substitution, optimization of morphology and carbon modification are highlighted. The perspectives of Mn-based electrode materials for future studies are also provided. We believe this review is important and helpful to explore and apply Mn-based electrode materials in aqueous sodium-ion batteries.
Nano-Micro Letters
2023, 15(1): 192
1 福州大学 先进制造学院,福建 晋江 362200
2 中国科学院半导体研究所,北京 100083
利用前后向有限差分算法，对锑化物带间级联激光器有源区结构InAs/GaSb/AlSb的电子态进行了理论计算与分析。研究了哈密顿量算符序、有效质量参数修正、内界面态对结构能态及波函数的影响。分析表明，导带有效质量参数取正值可以在两种算符序下有效抑制伪解产生，Burt-Foreman算符序下的跃迁能量更为合理。对于内界面采用缓变假设后，其跃迁能量计算值略高于陡变界面下的计算结果，二者的波函数在界面附近差异不明显。
带间级联激光器 8带包络函数模型 有限差分算法 算符序 界面 inter-band cascade lasers eight band envelope-function model finite difference method operator order interface
1 中国科学院空天信息创新研究院，北京 100094
2 中国科学院大学，北京 100049
3 粒子输运与富集技术全国重点实验室，天津 300180
通过实验和仿真的方法，研究了多点分布的内部热源加热作用对紧凑型双路TEA CO2激光器谐振腔热稳定性的影响。采用直流风扇热交换抑制了高压电源的局部加热效应，通过调整热交换的效率，可在13~22 ℃环境温度范围内，使前后谐振腔镜受到的局部加热形变作用和环境温度引起的热胀冷缩作用基本抵消。为实现更宽温度范围的谐振腔稳定性，在有效热交换措施的基础上，根据模拟预测的形变规律，提出了谐振腔变形的角度补偿方法。使用传感器获得环境温度与设定初始环境温度的偏差，通过调整伺服电机步数实现对方位角的补偿，补偿值约0.28 step/℃，通过PZT促动器调整悬臂调谐结构末端位移，实现对俯仰角的补偿，补偿值约0.79 μm/℃。
TEA CO2 激光器 局部加热效应 腔体形变 角度补偿 TEA CO2 laser local heat effect cavity deformation angular compensation 红外与激光工程
2023, 52(10): 20230020
