Widely and continuously tunable optical parametric generator based on MgO-doped periodically poled LiNbO3 crystal

A widely and continuously tunable optical parametric generator (OPG) pumped by a 1064-nm acoustooptically Q-switched diode-end-pumped Nd:YAG laser based on MgO-doped periodically poled LiNbO3 crystal with a multigrating structure (29.2-30.4 μm) is reported.A broad continuous signal spectrum of 1513-1700 nm is obtained by changing the crystal grating periods from 29.2 to 30.4μm and by tuning the crystal temperature from 30 to 180 ℃ simultaneously.When the average pump power is 1.82 W with pulse duration of about 70 ns operating at a repetition rate of 10 kHz,the maximum signal output power of the periodically poled MgO-doped lithium niobate (PPMgLN) OPG is about 210 mW corresponding to the idler and total powers of 118.4 and 328.4 mW respectively.     

Negative photoconductivity in low-dimensional materials

In recent years,low-dimensional materials have received extensive attention in the field of electronics and optoelectronics.Among them,photoelectric devices based on photoconductive effect in low-dimensional materials have a broad development space.In contrast to positive photoconductivity,negative photoconductivity(NPC)refers to a phenomenon that the conductivity decreases under illumination.It has novel application prospects in the field of optoelectronics,memory,and gas detection,etc.In this paper,we review reports about the NPC effect in low-dimensional materials and systematically summarize the mechanisms to form the NPC effect in existing low-dimensional materials.     

Majorana stellar representation for mixed-spin (s, 1/2) systems

By describing the evolution of a quantum state with the trajectories of the Majorana stars on a Bloch sphere,Majorana’s stellar representation provides an intuitive geometric perspective to comprehend the quantum system with highdimensional Hilbert space.However,the representation of a two-spin coupling system on a Bloch sphere has not been solved satisfactorily yet.Here,a practical method is presented to resolve the problem for the mixed-spin(s,1/2)system and describe the entanglement of the system.The system can be decomposed into two spins:spin-(s+1/2)and spin-(s?1/2)at the coupling bases,which can be regarded as independent spins.Besides,any pure state may be written as a superposition of two orthonormal states with one spin-(s+1/2)state and the other spin-(s?1/2)state.Thus,the whole initial state can be regarded as a state of a pseudo spin-1/2.In this way,the mixed spin decomposes into three spins.Therefore,the state can be represented by(2s+1)+(2s?1)+1=4s+1 sets of stars on a Bloch sphere.Finally,some examples are given to show symmetric patterns on the Bloch sphere and unveil the properties of the high-spin system by analyzing the trajectories of the Majorana stars on the Bloch sphere.     

All-silicon chiral metasurfaces and wavefront shaping assisted by interference

The usage of full-color imaging in digital pathology produces significant results. Compared with a grayscale image or a pseudocolor image containing contrast information, a full-color image can identify and detect the target object better with color texture information. Fourier ptychographic microscopy(FPM) is a high-throughput computational imaging technique that breaks the tradeoff between high resolution(HR) and a large field of view. It also eliminates the artifacts of scanning and stitching in digital pathology and improves its imaging efficiency. However, the conventional full-color digital pathology based on FPM is still time-consuming because of the repeated experiments with tri-wavelengths. A color transfer FPM approach termed "CFPM" was reported. The color texture information of a low-resolution full-color pathologic image is directly transferred to the HR grayscale FPM image captured by only a single wavelength. Both of the color space of FPM based on the standard CIE-XYZ color model and the display based on the standard RGB color space were established. Different FPM colorization schemes were analyzed and compared with 30 biological samples. Three types of evaluation approaches were provided, including the root-mean-square error(RMSE), the difference maps, and the image histogram cosine similarity. The average RMSE values of the conventional method and CFPM compared with the ground truth were 5.3% and 5.7%, respectively. Therefore, the reconstruction time is significantly reduced by 2/3 with the sacrifice of precision of only 0.4%. The CFPM method is also compatible with advanced fast FPM approaches to further reduce computation time.     

Mineral-derived Li4SiO4-based adsorbent for post-combustion CO2 capture: An experimental and kinetic investigation

Li₄SiO₄-based adsorbent is considered as a promising choice for the CO₂ removal from power plants’ flue gases. However, the relatively high raw materials cost still limits its industrial applications. In this work, aiming to reduce the cost of Si-source, three novel natural occurring minerals including the pumicestone, the montmorillonite and the attapulgite were employed as Si-sources for the production of Li₄SiO₄-based adsorbents. The phase composition, surface morphology as well as the cyclic CO₂ ad-desorption performance of obtained adsorbents were experimentally and kinetically investigated. It is found that the Si content of minerals directly determines the adsorption capacity of adsorbents, resulting in a relatively high and stable capacity of nearly 0.1 g/g within 22 cycles for the pumicestone derived adsorbent compared with other adsorbents obtained from minerals. Moreover, the excess Ca inside the minerals is found forming CaO, which is harmful to the desorption performance of adsorbent owing to the occurrence of Li–Ca–CO₂ interactions. As a consequence, Si-source with high Ca content was proven inadaptable for the synthesis of Li₄SiO₄-based adsorbent, which provides guidance for the future selection of mineral Si-sources in this field.     

通过类比Rice-Ramsperger-Kassel-Marcus理论再议Marcus的电子转移速率：关于线性和非线性溶剂化情形的统一形式

R. A. Marcus在他开拓性的工作中,考察了溶剂化效应对电子转移过程的影响,并给出了著名的非绝热电子转移速率公式. 本文基于热力学溶剂化势能面的分析,从Rice-Ramsperger-Kassel-Marcus理论的角度重新考察了Marcus的公式. 由类比Rice-Ramsperger-Kassel-Marcus得到的理论,不仅可以适用于线性溶剂化的情形并得到Marcus的速率公式,也同样可以用于非线性溶剂化的情形. 在非线性溶剂化的情形下,会存在溶剂化势能面的多点交叉. 本文平行地考察了Fermi黄金规则给出的相应结果,并对比本工作中所提出的Rice-Ramsperger-Kassel-Marcus类似理论进行了批判性的讨论. 作为例释,考察了二次型溶剂化的情形. 对于这种情形,物理上存在良好的描述方案.     

掺杂石墨烯改善环氧树脂机械性能和抗腐蚀性能的机理研究

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯和掺杂石墨烯对环氧树脂的吸附行为.主要研究了四种石墨烯:本征石墨烯(P-graphene)、B掺杂的石墨烯(B-graphene)、N掺杂的石墨烯(N-graphene)和O掺杂的石墨烯(O-graphene).结果表明,O掺杂有利于降低石墨烯对环氧树脂的吸附能.从电子结构上看,O掺杂的石墨烯与环氧树脂发生轨道杂化,且二者的电荷密度明显重叠,说明O掺杂的石墨烯与环氧树脂的相容性好.因此,在环氧树脂涂层中加入O掺杂的石墨烯有望成为一种提高环氧树脂涂层机械性能和抗腐蚀性能的方法 .     

A 2 μm Single-Longitudinal-Mode Ho:GdVO4 CW Laser

Journal of Russian Laser Research - We demonstrate a single-longitudinal-mode Ho:GdVO4 continuous-wave (CW) laser at 2048.6 nm. We achieved excellent single-longitudinal-mode performance using a...     

固体核磁共振技术在锡硅分子筛表征中的应用

生物质等绿色资源的高效转化利用是催化科学的重要发展方向.锡硅分子筛因具有优良的催化性能而得到相关研究者的普遍关注.准确构建催化剂活性中心结构/酸性与催化反应性能之间的构效关系是新型高效催化剂设计与研发的基础.固体核磁共振（NMR）是研究分子筛活性中心局域结构、酸特性与催化反应机理的重要手段.本文简述了近年来固体NMR技术在锡硅分子筛研究领域的一系列主要进展,并进行了展望.