ZnO:Fe3+体系局域晶格结构的研究

本文采用对角化三角场中d5组态离子的完全能量矩阵的方法,研究了Fe3+离子在ZnO:Fe3+体系的局域结构与EPR参量的关系,结果表明：在ZnO:Fe3+体系中,Fe3+取代了Zn2+离子后整个晶体显示出压缩畸变,其畸变参量ΔR=-0.119A和Δθ=0.339°被确定。     

Al2O3:Fe3+体系晶格局域结构的EPR理论研究

本文通过分析Al2O3∶Fe3+体系中Fe3+离子的EPR谱,研究Fe3+的局域晶体结构结果表明Al2O3∶Fe3+的局域结构存在各向异性膨胀.用拟合EPR谱的低对称参量D和(a-F)实验值的方法,求得两个三棱锥的棱与C3轴的夹角分别为θ1=46.54°和θ2=61.26°,相对于原Al2O3结构的畸变角分别是Δθ1=-1.1°±0.1°,Δθ2=-1.8°.两畸变角同时均小于0说明Al2O3∶Fe3+体系中含Fe3+离子的晶格主要产生沿C3轴的伸长畸变.     

Mn2+在CoSiF6·6（H2O）:Mn2+体系中EPR谱的理论研究

本文采用对角化三角场中d5电子组态的完全能量矩阵的方法,并同时考虑EPR的二阶参量D和四阶参量(a-F),研究了Mn2+在CoSiF6.6(H2O)体系的局域结构畸变.结果表明:在CoSiF6.6H2O:Mn2+体系中,Mn2+取代了Co2+离子后整个晶体显示出伸长畸变,并且其结构参数R=2.260,θ=52.5192°被确定.     

Al_2O_3∶Fe~(3+)体系晶格局域结构的EPR理论研究

本文通过分析Al2 O3 ∶Fe3 + 体系中Fe3 + 离子的EPR谱 ,研究Fe3 + 的局域晶体结构结果表明Al2 O3 ∶Fe3 + 的局域结构存在各向异性膨胀。用拟合EPR谱的低对称参量D和 (a -F)实验值的方法 ,求得两个三棱锥的棱与C3 轴的夹角分别为θ1=4 6 .5 4°和θ2 =6 1.2 6° ,相对于原Al2 O3 结构的畸变角分别是Δθ1=- 1.1°± 0 .1° ,Δθ2 =- 1.8°。两畸变角同时均小于 0说明Al2 O3 ∶Fe3 + 体系中含Fe3 + 离子的晶格主要产生沿C3 轴的伸长畸变     

掺杂晶体材料ZnGa_2O_4:Fe~(3+)局域结构畸变及其微观自旋哈密顿参量研究

基于Newman的晶场叠模型与微观自旋哈密顿理论,建立了ZnGa2O4:Fe3+晶体材料中磁性离子Fe3+局域结构与其自旋哈密顿(spin-Hamiltonian,SH)参量(包括二阶零场分裂(zero-field splitting,ZFS)参量D,四阶ZFS参量(a-F),Zeeman g因子:g//,g⊥,△g(=g//-g⊥))之间的定量关系.采用以全组态完全对角化方法为理论背景的CFA/MSH(Crystal Filed Analysis/Microscopic Spin Hamiltonian)研究软件,研究了ZnGa2O4:Fe3+材料中磁性离子Fe3+的SH参量与其局域结构的依赖关系.研究表明:对于ZnGa2O4:Fe3+晶体材料,当磁性离子Fe3+的局域结构畸变参数△R=0.0487 nm,△θ=0.192°时,其基态SH参量理论计算结果与实验测量符合很好,进一步表明Fe3+掺入晶体材料后将引起磁性Fe3+离子局域结构的微小畸变,但其仍然保持D3d点群对称局域结构.在此基础上研究分析了SH参量的微观起源,结果表明:ZnGa2O4:Fe3+晶体材料的SH参量主要来源于SO(spin-orbit)磁相互作用机理,来自其他磁相互作用机理(包括SS(spin-spin),SOO(spin-other-orbit),OO(orbit-orbit),SO-SS-SOO-OO)的贡献比较小.     

KZnF3:Fe3+体系局域晶体结构的理论研究

本文采用对角化三角场中d5组态完全能量矩阵的方法,研究了KZnF3Fe3+体系的局域晶体结构和EPR参量之间的关系.在分析中我们引入了双层配位模型,即配位体包括Fe3+离子最近邻的6个F-离子和次近邻的8个K+离子.计算表明KZnF3Fe3+的局域结构畸变源于一个K+离子沿C3轴方向(即[111]方向)向Fe3+离子的移动,从而诱导F-离子的位移,使得Fe3+-F-键与C3轴夹角发生变化.通过计算EPR的低对称参量D和(a-F),我们分别得出室温(T=300K)时的畸变角为△θ1=2.58°,△θ2=-1.4°和低温(T7=77 K)时畸变角为△θ1=2.85°,△θ2=-1.40计算结果与实验观察值△θ1=2.8±0.3°,△θ2=-1.1±0.3°相符合.     

ZnSiF66H2O∶Fe2+晶体光谱结构的杨特勒效应和电子顺磁共振g因子

研究了过渡金属络合物ZnSiF66H2O∶Fe2+晶体光谱结构的杨特勒效应和电子顺磁共振g因子。由单晶的中子衍射方法得到ZnSiF66H2O∶Fe2+的晶体结构,这种结构可以用SiF2-6和Zn(H2O)++∶Fe2+两个离子来描述。而局域三角对称的Zn(H2O)++∶Fe2+离子反映了这种晶体的主要光谱性质。利用不可约张量的理论构成了晶体场和自旋轨道相互作用哈密顿矩阵和电子顺磁共振理论公式,求出了晶体ZnSiF66H2O∶Fe2+中Fe2+离子的电子顺磁共振零场分裂参量(D,F-a)及g因子,并研究了低自旋3L态对电子顺磁共振零场分裂参量的贡献是不能忽略的,而对g因子的贡献是非常小的,并理论计算了它的晶体结构,证实了杨特勒效应的存在,理论计算的结果与实验值是相符的。     

常温下YGaG:Fe3+体系的EPR谱研究

本文采用对角化三角晶场中d5组态离子的完全能量矩阵的方法,研究了YGaG:Fe3 体系的EPR谱与局域晶格畸变的关系,利用EPR谱的低对称参量D和(a-F)的实验值确定出Fe3 离子在YGaG:Fe3 体系中的键长R=0.2005 nm,键角θ=51.498°,以及晶格畸变角Δθ=0.954°。     

氟钙钛矿AMF3:Fe3+晶体中Fe3+离子的零场分裂参量及晶格缺陷研究

对氟钙钛矿晶体AMF₃：Fe³⁺（A=K，Rb，Cs；M=Zn，Cd）四角对称占位的零场分裂（ZFS）进行分析，证实了晶格缺陷及畸变的存在．对ZFS参量随晶格畸变参量的变化关系进行了详细研究，考虑了缺陷及缺陷引起的晶格畸变两者的贡献，得出几种氟钙钛矿晶体的晶格畸变参量 关键词：     

ZnO晶体中Mn2+与Fe3+杂质中心的缺陷结构研究

用建立在强场图像和自旋轨道耦合机理的高阶微扰公式研究了ZnO晶体中Mn2+和Fe3+杂质中心的零场分裂.研究发现:Mn2+和Fe3+离子不能占据准确的Zn2+位置,而是沿c3轴方向各自位移一段距离ΔR.这些位移及与此相关的缺陷结构也为Newman叠加模型所证实 关键词： 零场分裂 ZnO晶体 晶格畸变 叠加模型     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.