周期和准周期超晶格固体薄膜表面吸附原子的共振荧光

本文使用表面修饰的光学Bloch方程,求得周期和准周期超晶格固体薄膜表面吸附原子的共振荧光谱,并研究了压缩效应。对该薄膜各层厚度和介电性质变化所带来的影响进行了讨论。同时,也对整个薄膜不同几何结构的影响进行了比较和分析。 关键词：     

驱动对光子晶体中原子自发辐射的影响

文章讨论了在驱动场作用下,三能级原子在光子晶体中的自发辐射问题。由于量子干涉和光的局域化作用,两个上能级中的布居数将具有周期振荡或准周期振荡的性质,     

驱动场对光子晶体中原子自发辐射的影响

文章讨论了在驱动场作用下, 三能级原子在光子晶体中的自发辐射问题.由于量子干涉和光的局域化作用,两个上能级中的布居数将具有周期振荡或准周期振荡的性质,这不仅与两个上能级与禁带的相对位置有关,同时也与原子的初始状态有关.驱动场的强度和入射位相也能控制光子晶体中三能级原子的自发辐射.     

周期条状结构中长程表面等离子激元噪声特性分析(英文)

基于表面等离子激元自发辐射放大噪声系数理论,研究了长程表面等离子激元噪声系数变化规律,设计了嵌有金属条的长程表面等离子结构.数值模拟得到表面等离子及周期条状长程表面等离子的噪声系数变化规律.给出入射波长从0.5μm到1.75μm,每隔0.25μm的噪声特性,发现随着波长的增加噪声系数趋近于常数.仿真结果表明:表面等离子及长程表面等离子自发辐射放大的噪声系数随着增益介质增大而明显增强;周期条状长程表面等离子结构中,随着金属膜厚度以及金属条高度及个数增加导致噪声系数增加,其中金属膜厚度对于其作用较明显.     

八重准周期排列的短沟槽结构减阻机理分析

设计构建了一排和三排阵列的八重准周期短条纹沟槽减阻结构,以及作为对比研究的无序和周期结构,并采用雷诺Navier-Stokes方程和RANGκ-ε湍流模型,系统计算了这些结构表面的湍流边界层状态和总应力,模拟结果显示:八重准周期沟槽结构相对于周期和无序结构具有更优的减阻效应,且为三排阵列时的减阻效果明显优于单排阵列,这一结果得到了减阻实验的验证,通过分析比较不同结构的流体边界层特性发现,八重准周期结构可有效抑制附面层的涡强度,减小湍流耗散速率,保持流体条纹相的稳定性,结合二维光栅的夫琅禾费衍射波模型分析表明,八重准周期结构可减弱衍射谱在大角度方向上的谱强度,揭示出该结构抑制流体相干扰动波扩展的物理机制,并与流场分析结果相符合。     

Davey-Stewartson方程组的包络周期解和孤立波解

应用Jacobi椭圆函数展开法,求得了Davey-Stewartson方程组的包络周期解和孤立波解． 关键词： Davey-Stewartson方程 Jacobi椭圆函数 包络周期解 孤立波解     

准分子激光器放大自发辐射特性的研究

本文考虑了XeCl激光振荡器中放大自发辐射对阈值条件和输出特性的影响,建立了激光和放大自发辐射归一化光通量的耦合输运方程,求得激光和放大自发辐射光通量分析和输出功率的解析表达式。结果表明:(1)放大自发辐射的存在增加了激光的阈值增益;(2)随着腔的Q值的提高,放大自发辐射的输出减弱;(3)适当地选取腔镜的反射率,即可有效地抑制放大自发辐射,从XeCl准分子激光器空间相干性的测量证实了上述结果。     

周期驱动下半导体动力学行为及控制

从nGaAs载流子非线性输运理论出发,建立物理模型,推导其动力学方程,分析系统随外场变化出现的复杂分支情况.数值模拟表明,在输入场幅值和频率变化的一定范围内,该系统具有周期、准周期和混沌特性,计算了表征混沌特性的物理量.利用间隙脉冲驱动法控制混沌得到预期的周期轨道 关键词： 分支 混沌 负微分电导     

广义Fibonacci准周期结构声子晶体透射性质的研究

提出了一维广义Fibonacci准周期结构的声子晶体模型. 对弹性波通过该一维准周期结构声子晶体的透射系数进行数值计算,并与周期结构和标准Fibonacci准周期结构声子晶体的透射系数进行比较. 结果表明,利用一维广义Fibonacci准周期结构的声子晶体可获得比周期结构和标准Fibonacci准周期结构声子晶体更大的带隙范围,同时在带隙内有更丰富的局域模式存在. 对局域模性质的研究有助于声波或弹性波滤波器的制作. 关键词： 广义Fibonacci准周期结构 声子晶体 局域化     

电子束沿多层膜表面运动时产生的电磁辐射

电子束沿多层膜表面运动时会产生自发辐射。分析自发辐射的精确波长公式、自发辐射中电子束品质的变化规律和电子自发辐射的功率后得出:电子束沿金属-介质多层膜表面运动时产生自发辐射,电子束内各种速度的电子数都按指数规律变化,实际电子束自发辐射的总辐射功率与金属-介质多层膜的空间周期成反比。     

含n＝k超薄金属膜的周期对称膜系的性质及窄带高反膜设计

本文阐述了n≈k的超薄金属膜与介质膜组成周期对称膜系的光学特性,并结合Ag、Al等膜层的高反特性提出了可见光区诱导窄带高反膜系结构,推导出膜系的反射率、反射峰值、反射半波带宽等光谱反射特性的近似公式,实验证实了理论设计和分析.同时也提出了设计红外和紫外窄带高反滤光片的方法.     

GREEN'S FUNCTION THEORY OF THE KONDO LATTICE(I) —MAGNETIC ORDERING AND KONDO EFFECT

The periodic s-d model is investigated by Green's function methods. A closed set of equations for Green's function of Kondo-lattice system and a formula of single electron self-energy are obtained in the presence of a broken rotational symmetry. The formula can-be used to discuss low temperature anomalous properties of Kondo-lattice system with spontaneous magnetization or in an external magnetic field. We have evaluated the influence of magnetic ordering on logarithmic sin-gularity of electron self-energy by perturbative method to Leading logarithmic order (LLO).The result obtained indiGates there exists a competition between Kondo effect and Zong range magnetic ordering. The static susceptibility in the paramagnetic case has been evaluated, too.     

Formation of thermocapillary structures in a heated liquid film

The conditions of formation of a three-dimensional thermocapillary structure on the surface of a liquid film flowing along a heater with the constant temperature were studied numerically based on the derived system of equations. Formation of the thermocapillary structure was modeled by periodic perturbations in the transverse direction superimposed on the two-dimensional flow. It is shown in calculations that transversal perturbations can develop into periodic rivulet structures on the film surface if the Marangoni number exceeds some threshold value. It is revealed that the rivulet structure develops when the period belongs to a certain range, which is determined by the value of Marangoni number. The results of calculations are in a good agreement with experimental data.     

Observation of modulated spontaneous emission of Rhodamine 6G in low refractive index contrast 1D-periodic gelatin film

The modulation of the spontaneous emission of Rhodamine 6G has been observed in one-dimensional periodic dielectric structure of dichromated gelatin film with refractive index contrast as low as 0.01. The spontaneous emission is enhanced at the band edges and inhibits in the band gap, which agree well with the theoretical analysis on the redistribution of the fractional local density of optical states.     

磁性薄膜的晶格结构和磁性

采用Monte-Carlo模拟方法对六边形、正方形和三角形晶格结构磁性薄膜的磁学特性及磁畴结构进行了模拟,结果表明,磁性薄膜的磁性特征及其磁相变温度和薄膜结构密切相关并存在临界膜厚,当薄膜厚度大于临界膜厚时薄膜磁性特征稳定.在低温区,不同结构磁性薄膜的磁滞回线均出现台阶现象,结果同相关实验一致.     

NON-LINEAR MODELLING OF ROTOR DYNAMIC SYSTEMS WITH SQUEEZE FILM DAMPERS—AN EFFICIENT INTEGRATED APPROACH

Squeeze film dampers used in rotor assemblies such as aero-engines introduce non-linear damping forces into an otherwise linear rotor dynamic system. The steady state periodic response of such rotor dynamic systems to rotating out-of-balance excitation can be efficiently determined by using periodic solution techniques. Such techniques are essentially faster than time marching techniques. However, the computed periodic solutions need to be tested for stability and recourse to time marching is necessary if no periodic attractor exists. Hence, an efficient integrated approach, as presented in this paper, is necessary. Various techniques have been put forward in order to determine the periodic solutions, each with its own advantages and disadvantages. In this paper, a receptance harmonic balance method is proposed for such a purpose. In this method, the receptance functions of the rotating linear part of the system are used in the non-linear analysis of the complete system. The advantages of this method over current periodic solution techniques are two-fold: it results in a compact model, and the receptance formulation gives the designer the widest possible choice of modelling techniques for the linear part. Stability of these periodic solutions is efficiently tested by applying Floquet Theory to the modal equations of the system and time marching carried out on these equations, when necessary. The application of this integrated approach is illustrated with simulations and an experiment on a test rig. Excellent correlation was achieved between the periodic solution approach and time marching. Good correlation was also achieved with the experiment.     

Spontaneous periodic structures induced in thin AgCl-Ag films by the continuum in the case of optical rotation of the plane of polarization

The formation of spontaneous periodic structures in thin AgCl-Ag films subject to the continuum (λ≈450–700 nm) in the case of rotation of the plane of polarization with the help of crystalline quartz is studied. The periodic structures are formed due to the excitation of waveguide TE₀ modes in spontaneous Rayleigh scattering of radiation with a wavelength λ incident on the film. The structure periods are smaller than λ and vary in proportion with λ. After special treatment of the irradiated sample (fixing and deposition of an Al layer), periodic structures form a thin reflection hologram capable of reproducing the direction of linear polarization, the angle of optical rotation, and the color of the spectrum recorded. The study of diffraction patterns and small-angle scattering from small portions of a hologram, which were exposed to light with various wavelengths in the recording process, with the help of a probing UV beam (λ_p=337 nm), made it possible to reveal special features of the manifestation of Rayleigh and Wood anomalies associated with the domain structure of PS.     

Spontaneous parametric transition from periodic motion to chaos in a dynamical system with two degrees of freedom

A study is made of a spontaneous parametric transition to chaos by the disruption of periodic motion in a generating structure with two degrees of freedom. A comparison of the properties of the system examined in this study and the properties of objects with an infinite-dimensional phase space shows the universality of the spontaneous parametric scenario for a loss of stability of periodic motion that leads to randomization of the oscillatory process. Tomsk University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 2, pp. 91–95, February, 1999.     

Spatial ordering of defects by laser irradiation

A closed mathematical model is constructed for the kinetics of processes in laser-irradiated crystals, including a system of nonlinear equations for the temperature and strain fields and for the point-defect density. Two types of instability are considered: diffusion-strain and recombination-strain. Criteria for their onset are obtained. Formation of a periodic structure of point defects in a thin film is analyzed.Translated from Preprint No. 88 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.