波长缩放高频调制全息成象公式的校正

本文给出了高频调制具有波长缩放全息成象公式的校正系数.由校正后的公式计算的成象点,其衍射角及坐标值可获得精确的结果.验证表明,计算的坐标值与实际的坐标值之差保持在0.4％左右.并给出了当μ≤1时由校正系数直接计算x_3ν和y_3ν的简便公式. 关键词：     

计算机产生全息光学元件用于校正椭圆高斯激光束

本文讨论了计算机产生全息光学元件,用以校正椭圆高斯激光束,计算这个全息光学元件的详细数学方程已作了推导,由计算机控制绘图机绘制了全息图,缩制了全息光学元件,并得出了实验结果。 关键词：     

Computable error bounds for pointwise derivatives of a Neumann problem

In this paper we discuss the recovery of derivatives and thecomputation of rigorous and useful upper bounds for the pointwiseerror in the recovered derivatives, for finite element approximationsof the Laplace equation with Neumann boundary conditions, especiallyat points close to or on a smooth, curved boundary. We analyzethe dipole image technique for the case of curved boundaries,and show how to compute reliable recovered derivatives and errorbounds even in the limiting case of points lying on the curvedboundary. Numerical experiments show reasonably tight errorbounds for points both close to and away from a curved boundary.     

Self-assembled growth of nanostructural Ge islands on bromine-passivated Si(111) surfaces at room temperature

We have deposited relatively thick (∼60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanov growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are variations in the details of the island size distribution.