Manipulation of the overall polarization orientation in the focal volume of high numerical objectives

We propose an approach for tuning the three-dimensional polarization of a focusing subwavelength spot by a high numerical aperture objective. The incident beams are composed of a radially polarized beam, an azimuthally polarized beam, and a linearly polarized beam with three different weighting factors, respectively. A specially designed adjustable amplitude angular selector is also inserted at the back aperture of the objective for tuning the polarization azimuthally. It is shown that any desired overall polarization orientation can be obtained. We calculated the overall polarization orientation in the focal volume. It is found that the polar angle of the overall polarization orientation can be arbitrarily tuned by the combination of a radially polarized beam and a linearly polarized beam with different weighting factors, and the azimuthal angle can be tuned by rotating the orientation of the linearly polarized beam azimuthally.     

Production of annular flat-topped vortex beams

A model of an annular flat-topped vortex beam based on multi-Gaussian superimposition is proposed.We experimentally produce this beam with a computer-generated hologram(CGH) displayed on a spatial light modulator(SLM).The power of the beam is concentrated on a single-ring structure and has an extremely strong radial intensity gradient.This beam facilitates various applications ranging from Sisyphus atom cooling to micro-particle trapping.     

Aun(n=2-9)团簇与乙醇分子相互作用的第一性原理研究

利用密度泛函理论研究了Au_n(n=2-9)团簇吸附一个乙醇分子的结构和电子性质. 研究结果表明: Au_n(n=2-9)团簇的最稳定构型为二维平面结构, Au6团簇最稳定; 吸附过程是通过金团簇上一个特定的金原子与乙醇分子中氧原子相互作用完成, 形成了20种稳定构型; 金原子的配位数对吸附作用影响明显; 作为吸附主体的金团簇和被吸附的乙醇分子在吸附前后构型无明显变化, 它们之间为弱相互作用.     

Restoration of Decentered Gaussian Beam with the Combination of a Lens and a Gaussian Aperture

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全视差二步彩虹全息

提出一种利用正弦光栅的色散特性 ,并用两步记录法制作全视差彩虹全息的方法。由于未使用狭缝限制物光波 ,再现像无垂直视差损失 ,也无需在狭缝像位置观察。     

球面折射系统和复合厚透镜的分数傅里叶变换

提出单球面折射系统可以作为光学分数傅里叶变换的最基本单元。在此基础上可以构造多种厚透镜或复合厚透镜分数傅里叶变换系统。推导了系统结构参数与分数傅里叶变换的级次的关系。指出单球面折射系统及其构造的透镜系统对输入物函数的分数傅里叶变换输出可以位于自由空间,也可在球面折射材料内部或折射材料端面。输出平面位置的灵活性及其构造复杂系统的多样性,对于分数傅里叶变换的应用和光学信息处理必定具有潜在的实用价值。     

聚焦径向调制Bessel-Gaussian光束实现亚波长尺寸纵向偏振光束

亚波长尺寸纵向偏振光束在粒子加速,单个分子偶极矩测量,二次谐波成像和纵向偏振共焦显微镜等方面有非常广泛的应用.本文提出径向调制的Bessel-Gaussian光束模型,经高数值孔径显微物镜聚焦可以获得高纯度的纵向偏振光束.利用矢量衍射理论数值模拟了焦点附近光强分布、磁场分布和能流密度空间分布.结果表明光斑半高全宽度可以达到0.4λ.该方法无需环形孔径或环形相位滤波器,光能利用率高,分辨率好,达到改进各种应用的效果. 关键词： Bessel-Gaussian光束 纵向偏振光束 聚焦 亚波长     

Tight focus of a radially polarized and amplitude- modulated annular multi-Gaussian beam

The focusing of a radially polarized beam without annular apodization ora phase filter at the entrance pupil of the objective results in a wide focus and low purity of the longitudinally polarized component. However, the presence of a physical annular apodization or phase filter makes some applications more difficult or even impossible. We propose a radially polarized and amplitude-modulated annular multi-Gaussian beam mode. Numerical simulation shows that it can be focused into a sharper focal spot of 0.125λ² without additional apodizations or filters. The beam quality describing the purity of longitudinally polarized component is up to 86%.     

Detour phase Talbot array illuminator

In this Letter, we propose a simple and effective approach for transforming a conventional Talbot array illuminator(TAI) with multilevel phase steps into a binary-phase TAI(BP-TAI) through detour phase encoding. The BP-TAI is a binary(0 π) phase-only diffractive optical element, which can be utilized to generate a large-scale focal spots array with a high compression ratio. As an example, we design a square BP-TAI with the fraction parameter β = 15 for achieving a square multifocal lattice with a high compression ratio β~2.Theoretical analysis and experimental results demonstrate that the detour phase encoding is efficient for designing the BP-TAI, especially with the high compression ratio. Such results may be exploited in practical large-scale optical trapping and X-ray imaging.