Investigation on the Interaction of Laser Beam and Metal Powders Conveyed by Coaxial Powder Feeder

In order to investigate the transient thermal stress field in wall-shape metal part during laser direct forming, a FEM model basing on ANSYS is established, and its algorithm is also dealt with. Calculation results show that while the wall-shape metal part is being deposited, in X direction, the thermal stress in the top layer of the wall-shape metal part is tensile stress and in the inner of the wall-shape metal part is compressive stress. The reason causing above-mentioned thermal stress status in the wall-shape metal part is illustrated, and the influence of the time and the processing parameters on the thermal stress field in wall-shape metal part is also studied. The calculation results are consistent with experimental results in tendency.

半导体激光器芯片频率响应的测量方法

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输出波形可调密集波分复用系统集成器件

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小尺寸氮化镓基蓝、绿色发光二极管管芯的制作方法

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波长可调谐分布布拉格反射半导体激光器的制作方法

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单模微腔半导体激光器

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垂直腔面发射激光器的光收发一体模块

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垂直腔面发射激光器列阵的并行光发射模块及制作方法

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提高n型硅原位掺杂载流子浓度的方法

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氮化镓基发光二极管管芯的制作方法

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氮化镓基发光二极管N型层欧姆接触电极的制作方法

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具有平顶和陡边响应的半导体光电探测器及实现方法

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Investigation of spectral bandwidth of optical parametric amplification

The spectral bandwidth of three-wave-mixing optical parametric amplification has been investigated. A general mathematical model for evaluating the spectral bandwidth of optical parametric amplification is developed with parametric bandwidth and gain bandwidth via three-wave noncollinear interactions. The spectral bandwidth is determined by expanding the wave-vector mismatch in a Taylor series and retaining terms through second order. The model takes into account the effects of crystal length, noncollinear angle, group velocity, group-velocity dispersion and gain coefficient. The relation between parametric bandwidth and gain bandwidth is clearly defined. The model is applied to a BBO OPA, a LBO OPA and a CLBO OPA.

Characteristics of beam profile of Gaussian beam passing through an axicon

Bessel beam can overcome the limitation of the Rayleigh range of Gaussian beam with the same spot size propagation without any spreading due to diffraction, which is considered as an useful function in guiding particles in the next generation of optical tweezers. The mathematical description of the Bessel beam generated by an axicon is usually based on the Fresnel diffraction integral theory. In this paper, we deduce another type of analytic expression suitable for describing the beam profile generated from the axicon illuminated by the Gaussian beam based on the interferential theory. Compared with the Fresnel diffraction integral theory, this theory does not use much approximation in the process of mathematical analysis. According to the derived expression, the beam intensity profiles at any positions behind the axicon can be calculated not just restricted inside the cross region as the Fresnel diffraction integral theory gives. The experiments prove that the theoretical results fit the experimental results very well. (C) 2004 Elsevier B.V. All rights reserved.

蒙特卡洛法在HIRFL-CSR钛升华泵设计中的应用

介绍了用蒙特卡洛法计算HIRFL CSR钛升华泵对于不同气体吸附系数在分子流条件下的吸附概率,并分析了挡板的形状、位置设置对于吸附概率的影响。通过实验测试,发现HIRFL CSR钛升华泵对H2的抽速与计算值接近,证明用蒙特卡洛法模拟计算、设计钛升华泵是可行的。