Hole Rashba effect and g-factor in InP nanowires

The hole Rashba effect and g-factor in InP nanowires in the presence of electric and magnetic fields which bring spin splitting are investigated theoretically in the framework of eight-band effective-mass envelop function theory, by expanding the lateral wave function in Bessel functions. It is well known that the electron Rashba coefficient increases nearly linearly with the electric field. As the Rashba spin splitting is zero at zero k(z) ( the wave vector along the wire direction), the electron g-factor at k(z) = 0 changes little with the electric field. While we find that as the electric field increases, the hole Rashba coefficient increases at first, then decreases. It is noticed that the hole Rashba coefficient is zero at a critical electric field. The hole g-factor at k(z) = 0 changes obviously with the electric field.

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.

中国沿岸上升流的研究

本文针对中国沿岸上升流研究现状，按上升流主要形成因子的不同将中国沿岸上升流系统地划分为两类，即以风为主要因子的风生类和以地形，海流共同作用为主要因子的地形-海流类。文中对各具体海区上升流的形成特点作了系统的归纳和分析。分类过程中还特别对两类中各具代表性的浙江和琼东沿岸上升流的形成特点进行了较为细致的探讨，进一步证实了浙江沿岸上升流与台湾暖流的密切关系，并得出了琼东沿岸上升流的强弱变化与盛行风变化一致的结论。文中还根据中国沿岸自然环境，提出了一个线性倾斜陆架地形上的上升流解析模式。该模式中，第一次同时考虑了风应力，海面坡度和斜压效应等因子对上升流形成的影响，并以虚宗量Bessel函数作为基本函数，给出了一组确定垂直流速的级数形式的解。该解可独立地分为三部分，分别表示风应力、海面坡度和斜压效应对上升流的贡献大小。模式中可将对沿岸上升流的研究归结为特殊函数的研究。在风区宽度任意可变情况下，用该模式得到的解能够比较精确地研究近岸和远岸海水垂直运动的变化情况，对模式的初步讨论表明，地形、风应力大小和风区宽度变化等因子对上升流的。形成都有重要影响。