Understanding periodically twinned structure in nano-wires

Using first-principles calculations we have investigated the high stability of twinned nano-wires, which explains why the stacking faults always appear. Furthermore, we present a growth model to describe the formation mechanism of the stacking faults in the compound nano-wire with zinc-blende structure (e.g. SiC). And the model is confirmed by the numerical calculation based on the point charge approximation.     

A method for determining optical constants, dimensions, and concentrations of “soft” absorbing particles in the brightening band region

We investigate the possibilities of creating a method for estimating the optical constants, dimensions, and concentrations of “soft” absorbing particles by applying a theoretical analysis of the angular dependence of the intergrated indicatrix, overall characteristics of light scattering, and absorption on the phase shift and diffraction parameter of particles in the brightening band region. We show that using the investigated optical characteristics, it is possible to determine the unknown parameters of a suspension from experimental data. Institute of Biophysics, Siberian Branch of the Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 807–812, November–December, 1997.     

基于有限差分光束传播法的过渡波导功耗分析

为了在既定尺寸下减小斜坡波导和弯曲波导的功耗，设计了4种过渡波导形状函数。用有限差分光束传播法(FD-BPM)进行了模拟分析，发现过渡波导形状的选取与坡度和曲折角存在条件有关，并给出了条件表达式及其详细说明。     

Photonic crystal channel drop filters with mirror cavities

In this paper, a new channel drop filter in two dimensional photonic crystals with mirror cavities is proposed. In the structure, three cavities are used. One is used for a resonant tunneling-based channel drop filter. The others are used to realize reflection feedback in the bus waveguide, which consists of a point defect micro-cavity side-coupled to a waveguide. The simulation results by using the finite-difference time-domain method conclude 98% output efficiency.     

一种硅基SiO2波导耦合器的设计与分析

波导耦合器是组成光纤传感系统和光纤通信系统光收发组件及模块的重要元器件,是实现光收发模块一体化光电集成的基础。给出了一种用光纤陀螺系统的X型四端口波导耦合器的工作原理,采用有效折射率法和BPM(Beam propagation method)法建立了耦合器的数学模型,计算并分析了耦合器尺寸在尽可能小的情况下和在满足单模传输的条件下耦合器的耦合系数、有效耦合长度、分光比以及回波损耗等参数之间的关系,并对其关键技术进行了系统的研究。仿真结果表明,所设计的波导耦合器在低损耗情况下分光比可达到50%∶50%,耦合器全长为33.5mm,输入输出波导间距为410μm,芯层截面积为6μm×6μm。     

Electrical generation of pure spin current with oscillating spin-orbit interaction

We propose an electrical scheme for the generation of a pure spin current without a charge current in a two-terminal device, which consists of a scattering region of a two-dimensional electron gas (2DEG) with Rashba (R) and/or Dresselhaus (S) spin-orbit interaction (SOI) and two normal leads. The SOI is modulated by a time-dependent gate voltage to pump a spin current. Based on a tight-binding model and the Keldysh Green’s function technique, we obtain the analytical expression of the spin current. It is shown that a pure spin current can be pumped out, and its magnitude could be modulated by device parameters such as the oscillating frequency of the SOI, as well as the SOI strength. Moreover, the spin polarisation direction of the spin current could also be tuned by the strength ratio between RSOI and DSOI. Our proposal provides not only a fully electrical means to generate a pure spin current but also a way to control the spin polarisation direction of the generated spin current.     

Deterministic separation of arbitrary photon pair states in integrated quantum circuits

Entangled photon pairs must often be spatially separated for their subsequent manipulation in integrated quantum circuits. Separation that is both deterministic and universal can in principle be achieved through anti‐coalescent two‐photon quantum interference. However, such interference‐facilitated pair separation (IFPS) has not been extensively studied in the integrated setting, which has important implications on performance. This work provides a detailed review of IFPS and examines how integrated device dependencies such as dispersion impact separation fidelity and interference visibility. The analysis applies equally to both on‐chip and in‐fiber implementations. When coupler dispersion is present, the separation performance can depend on photon bandwidth, spectral entanglement and the dispersion. By design, reduction in the separation fidelity due to loss of non‐classical interference can be perfectly compensated for by classical wavelength demultiplexing effects. This work informs the design of devices for universal photon pair separation of states with tunable arbitrary properties.

     

物理实验中测温热电偶冷端补偿方法的改进

本文介绍了两种热电偶冷端温度补偿电路在物理实验测量中的应用及校准方法,对热电偶的工作原理、冷端温度补偿必要性作了说明,并详细介绍了冷端温度补偿过程．     

离焦激光直写的线宽稳定方法

为了提高激光直写加工衍射光学元件时的线条质量,提出一种离焦激光直写的线宽稳定方法.该方法通过同时调节激光功率和离焦量,使光刻胶的曝光阈值处于线宽对曝光量的变化率较小位置,从而可以弱化线宽对实际曝光量或光刻胶阈值等变化的敏感度,提高利用离焦方法进行衍射光学元件制作时的线宽稳定性.推导了稳定线宽后的光功率控制模型和线宽模型,模型中的变量仅为离焦量,降低了光功率控制的复杂性.利用632.8 nm的He-Ne激光和NA-0.1的物镜在CCD上对采用该方法后的离焦线宽模型进行验证,实验结果与理论模型吻合较好.该方法对于线宽稳定度较高的衍射光学元件制作具有重要价值.     

Surface effect on the GSF energy of Al

The second-nearest-neighbor modified embedded atom method (2NN-MEAM) is used to calculate the generalized stacking fault (GSF) energy for (1 1 1) surface of Al crystal. It is found that the GSF energy curve is much lower for the fault in the first layer of the (1 1 1) surface than that in the bulk. When the fault exists in the second layer, the energy curve becomes considerably on the verge of that in the bulk. With a much lower unstable stacking fault energy γ_usf, the dislocation should be easier to set on at the outermost of the free surface. Expansion in relaxation always exists for the stacking fault either in bulk or near the surface and the GSF energy increases with the vertical expansion.