Cr∶LiSAF再生放大系统

设计了灯抽运Cr∶LiSAF(Cr∶LiSrAlF6)飞秒再生放大系统 ,对 80fs光脉冲 (展宽后约 10 3ps)进行了再生放大研究 ,获得了再生放大的输出能量与输入能量和放大倍率与放大往返次数间的关系 ,得到了 8× 10 5的放大倍率和 0 4mJ的单脉冲再生放大输出     

Cr∶ LiSAF 激光器的研究进展

按Cr∶ LiSAF 激光器的三种运转方式简要综述了国内外的发展状况,分析了各自的一些特点和应用及研发前景,并比较详细地说明了几个典型,最后,指出了我国发展激光二极管泵浦Cr∶ LiSAF 晶体的发展方向。     

被动Q调制Er∶Cr∶YSGG固体激光器

由于其3μm左右独特的激光波长,掺铒固体激光器(Er∶Cr∶YSGG激光器:λ=2.79μm;Er∶YAG激光器:λ=2.94μm)得到广泛的研究。通过采用在GaAs基底上生成的InAs薄膜作为被动调Q的饱和吸收体,实现了Er∶Cr∶YSGG激光Q调制输出。稳定的单脉冲调Q运转的抽运阈值为21J,最短脉冲宽度将近300ns,单脉冲运转能量可达20.3mJ。实验中所用的耦合输出镜均采用的是平-平的介质膜镜片,在2.79μm处的透射率为28%,全反镜是平-凹镀金镜片,曲率半径为2m,采用闪光灯抽运,脉冲宽度为150μs,激光工作频率为1Hz,激光增益介质为直径4mm,长度110mm的Er∶Cr…     

Nd∶GdCOB和Cr∶Nd∶GdCOB晶体的脉冲激光特性

Ca4GdO(BO3)3(GdCOB)是一种新型的自倍频晶体.利用氙灯作泵浦源,对单掺的Nd∶GdCOB和双掺的Cr∶Nd∶GdCOB两种自倍频晶体实现了1061nm～530.5nm自由运转的自倍频转换.单掺和双掺晶体的泵浦阈值能量分别为1.0J和0.92J,自倍频光的最大输出能量分别为1.96mJ和2.46mJ.利用脉冲染料激光作泵浦源,对Nd∶GdCOB晶体获得了1331nm基频光和655nm自倍频红光运转,并获得了530.5nm自倍频绿光输出.     

Mn∶Fe∶LiNbO3晶体光折变效应的研究

在LiNbO3中掺入Fe2O3和MnCO3生长Mn∶Fe∶LiNbO3晶体,对晶体进行极化处理及氧化还原处理.测试晶体的吸收光谱、指数增益系数、衍射效率和有效载流子浓度.结果表明,经还原处理的Mn∶Fe∶LiNbO3晶体是优良的全息存储介质材料.     

LD 泵浦的Cr4 + ∶YAGPNd∶YLF 激光器

文中介绍的小型LD 端面泵浦的Nd∶YLF 激光器,采用Cr4 + ∶YAG作为被动Q 开关,在1 -100Hz 的重复频率下可以实现脉冲能量30～40μJ ,脉宽4～5ns 的1053nm 的单纵模激光脉冲输出。     

连续Cr4+∶YAG激光器

Ｃｒ4 + ∶ＹＡＧ晶体的受激辐射在 12 5 0～ 15 80ｎｍ近红外波段 ,正是光纤通信的低损耗窗口 ,因此Ｃｒ4 + ∶ＹＡＧ激光器在光通信研究领域有应用前景。图 1实验装置图Ｆｉｇ .1Ｅｘｐｅｒｉｍｅｎｔａｌｓｅｔ ｕｐ　　本实验小组用掺Ｃｒ4 + 浓度为 2 .5× 10 17/ｃｍ3 的     

用Cr∶YAG被动调Q的Yb∶YAG激光

用连续钛宝石激光器作抽运源 ,在室温下用Cr4 +∶YAG作可饱和吸收体实现了Yb∶YAG晶体的被动调Q激光输出。实验中获得了在 1 0 3μm平均功率为 5 5mW和脉宽 (FWHM )为 0 35 μs的被动调 Q激光。Cr∶YAG的初始透过率对Yb∶YAG被动调 Q 激光的脉宽 (FWHM )和重复率有一定影响。实验表明Yb∶YAG晶体是一种有前景的结构紧凑、高效和全固化的被动调Q激光晶体。     

Ce∶Mn∶LiNbO3晶体紫外记录研究

采用紫外光作记录光在Ce∶Mn∶LiNbO3晶体中实现非挥发全息记录,灵敏度可达0.0803 cm/J,衍射效率(固定)为5.07%,比采用红光为记录光,紫外光为敏化光的非挥发双中心记录方案均提高了50多倍。分析表明,采用紫外光作为记录光,深能级电子被激发比例极大提高,参与光折变过程的电子平均运动周期变短,提高了衍射效率和灵敏度;深浅能级电子光栅的同相位,使得固定空间电荷场变强。文中还研究了退火对记录性能的影响。     

First principle study of spintronic properties for double perovskites Ba2XMoO6 with X=V,Cr and Mn

Cubic double perovskites Ba₂XMoO₆ (X=V, Cr and Mn) compounds are studied using the full potential linearized augmented plane wave (FP-LAPW) method within the frame work of density functional theory (DFT). The structural, electronic and magnetic properties are calculated by using the Generalized Gradient Approximation (GGA), GGA+U and modified Becke–Johnson mBJ-GGA. Density of States and band structure results reveal a similar half-metallic ferromagnetic ground state for Ba₂CrMoO₆. Whereas, a metallic ferromagnetic character is predicted for Ba₂VMoO₆ and a matching metallic ferromagnetic ground state is obtained for Ba₂MnMoO₆. The mBJ calculations yield a better energy-gap than the GGA and GGA+U methods.     

Efficient and Photostable ZnS‐Passivated CdS:Mn Luminescent Nanocrystals

Efficient and photostable ZnS‐passivated CdS:Mn (CdS:Mn/ZnS core/shell) nanocrystals were synthesized using reverse micelle chemistry. CdS:Mn/ZnS core/shell nanocrystals exhibited much improved luminescent properties (quantum yield and photostability) over organically (n‐dodecanethiol‐) capped CdS:Mn nanocrystals. This is the result of effective, robust passivation of CdS surface states by the ZnS shell and consequent suppression of non‐radiative recombination transitions. The dependence of photoluminescence (PL) intensity has been observed as a function of UV irradiation time for both organically and inorganically capped CdS:Mn nanocrystals. Whereas organically capped CdS:Mn nanocrystals exhibit a significant reduction of PL intensity, CdS:Mn/ZnS core/shell nanocrystals exhibit an increased PL intensity with UV irradiation. XPS (X‐ray photoelectron spectroscopy) studies reveal that UV irradiation of CdS:Mn/ZnS nanocrystals in air atmosphere induces the photo‐oxidation of the ZnS shell surface, leading to the formation of ZnSO₄. This photo‐oxidation product is presumably responsible for the enhanced PL emission, serving as a passivating layer.     

二氧化硅壳层对CdS:Mn/ZnS量子点的光稳定性影响研究

在量子点表面包覆二氧化硅壳层,能够有效的保护纳米粒子核不受外界环境的影响,使得它在光电子器件和生物标记等领域中有着广泛的应用前景。通过一锅法制备高质量CdS:Mn/ZnS量子点,然后利用反相微乳液方法在量子点的表面继续包覆SiO2层,得到CdS:Mn/ZnS@SiO2多层核壳结构量子点材料。化学性质稳定的ZnS及SiO2材料的包覆使CdS量子点材料的毒副作用降低并有效提高其稳定性,然而CdS:Mn/ZnS量子点的大部分性能在包覆SiO2后都保持不变,因此CdS:Mn/ZnS@SiO2量子点在光学应用中有很大的应用潜力。     

Band gap tailoring and yellow band emission of Cd0.9−xMnxZn0.1S (x=0 to 0.05) nanoparticles: Influence of Mn concentration

Cd_0.9-xMn_xZn_0.1S nanoparticles with x=0 to 0.05 were prepared by a simple chemical co-precipitation method at room temperature. Crystal structure and optical properties of the synthesized nanoparticles have been analyzed by X-ray diffraction (XRD) and UV–visible spectrophotometer. XRD confirmed the phase singularity of the synthesized material, which also confirmed the formation of Cd–Mn–Zn–S solid solution rather than secondary phase formation. Energy dispersive X-ray spectra showed the presence of Cd, Zn, Mn and S in the synthesized samples. The observed higher absorbance and lower transmittance of Mn-doped Cd_0.9Zn_0.1S than Cd_0.9Zn_0.1S is due to the size effect and also the defect states induced by Mn. The decrease in energy gap at Mn=0.01 is due the ‘sp–d’ exchange interactions between band electrons in CdS and the localized ‘d’ electrons of the Mn²⁺ ions. The increase in energy gap after Mn=0.01 can be explained by the excessive carriers generated by the impurity atoms. Fourier transform infrared spectroscopy (FTIR) illustrated the vibration modes of Cd–Zn–Mn–S between the wave number 530 cm⁻¹ and 780 cm⁻¹. Mn=0.01 doped sample exhibits a relatively high PL intensity and covers most of the visible region than the other samples; so desirable for LED application. The intensity ratio of the green band (GB) to Mn-related yellow band (YB) is decreased after Mn=0.01 which may be due the size effect or reduction of surface defect at higher doping concentrations.     

Synthesis and optoelectronic properties of silver-doped n-type CdS nanoribbons

Sliver doped n-type CdS nanoribbons (NRs)were successfully synthesized by using Ag2S as the dopant via a thermal co-evaporation method. The CdS:Ag NRs have wurtzite single-crystal structure with growth direction of [110]. Significantly, the conductivity of the CdS NRs increased ～6 orders of magnitude by silver doping. Moreover, the Ag doped CdS NRs showed much enhanced photoconductivity compared with the undoped ones, which will greatly favor the application of CdS nanostrucures in high-performance nano-optoelectronic devices.     

Ab initio study of electronic structure and magnetic properties in ferromagnetic Sr1−x(Mn,Cr)xO alloys

A first-principles approach is used to study the structural, electronic and magnetic properties of Sr_1−x(Mn, Cr)_xO alloys. The investigation was done using the (FP-LAPW) scheme within the generalized gradient approximation by Wu and Cohen (GGA-WC), GGA+U and LSDA+U. At ambient conditions our calculated results of band structures reveal that for Sr_1−x(Mn, Cr)_xO (for x=0.25 and 0.75) has a half-metallic (HM) band structure profile showing 100% spin polarization at the Fermi level. Therefore, the Sr_1−x(Mn, Cr)_xO (for x=0.25 and 0.75) is a candidate material for future spintronic/magnetoelectronics applications.     

锰掺杂对钛酸锶铅铁电薄膜带-带跃迁和带尾吸收特性的影响

通过透射光谱研究了锰掺杂量对钛酸锶铅铁电薄膜光学特性尤其是带-带跃迁和带尾吸收特性的影响,并利用柯西色散关系获得了光学透明区的光学常数.研究表明:随着锰掺杂量的增加,钛酸锶铅铁电薄膜的禁带宽度减小而带尾能增加.禁带宽度随锰掺杂的收缩可以归因为锰3d轨道降低了导带底的能级及掺杂后晶格的减小.掺杂锰离子的随机占位和非等价掺杂后氧空位浓度的增加则是导致局域带尾态拓宽的主要原因.     

Conversion of red and infrared luminescence centers as a result of electron bombardment and annealing of CdS and CdS:Cu single crystals

The luminescence centers and their conversion as a result of electron bombardment and annealing in CdS single crystals which were not specially doped and which were doped with copper have been investigated. The Cu atoms, which interact mainly with defects in the cadmium sublattice, form Cu_Cd, which are responsible for luminescence at wavelengths λ_m=0.98−1.00 μm. At annealing temperatures above 50 °C, conversion of the defect complexes, which are responsible for the green (λ_m=0.514 μm), red (λ_m=0.72 μm), and infrared (λ_m=0.98 μm) luminescence, occurs as a result of an increase in the mobility of point defects in the cadmium and sulfur sublattices of CdS:Cu. Fiz. Tekh. Poluprovodn. 31, 1013–1016 (August 1997)     

基于第一性原理的铁/铬掺杂单层MoS2电磁特性研究

文中利用第一原理计算,发现Cr/Feδ型掺杂是一种调节单层MoS₂的电磁特性的有效方法。区别于铁磁半金属,Feδ型掺杂MoS₂、Cr和Fe交替δ型共掺杂MoS₂呈现半金属亚铁磁性。Cr和Fe的3d轨道与其最近邻S的p态强耦合,其之间的虚拟跃迁遵循GKA规则。因此,Cr和Fe之间的反铁磁超交换相互作用产生了系统的亚铁磁性质。结果表明,单层MoS₂中的三维δ型掺杂提供了一种产生一维自旋极化传输通道的有效途径。     

Photosensitization of TiO2 Nanostructures with CdS Quantum Dots: Particulate versus Tubular Support Architectures

TiO₂ nanotube arrays and particulate films are modified with CdS quantum dots with an aim to tune the response of the photoelectrochemical cell in the visible region. The method of successive ionic layer adsorption and reaction facilitates size control of CdS quantum dots. These CdS nanocrystals, upon excitation with visible light, inject electrons into the TiO₂ nanotubes and particles and thus enable their use as photosensitive electrodes. Maximum incident photon to charge carrier efficiency (IPCE) values of 55% and 26% are observed for CdS sensitized TiO₂ nanotube and nanoparticulate architectures respectively. The nearly doubling of IPCE observed with the TiO₂ nanotube architecture is attributed to the increased efficiency of charge separation and transport of electrons.