夫琅禾费衍射的光谱特性

基于MATLAB语言,以夫琅禾费衍射为研究对象,数值模拟了夫琅禾费圆孔衍射和单缝衍射光谱特性,通过改变狭缝宽度和入射波的波长,数值模拟得到夫琅禾费单缝衍射的光强变化图和光谱特性图。结果表明,圆孔衍射的光强比单缝衍射的光强曲线在次级明纹的强度更加低,夫琅禾费衍射的结论与实际理论和试验吻合的较好。研究结果为夫琅禾费衍射的研究提供参考。     

单色仪转角重复精度的相位板衍射准直方法测量

为准确测量上海光源软X射线谱学显微光束线采用的变包含角平面光栅单色仪的转角重复精度,提出了一种新的基于相位板衍射准直技术的测量方法.该方法将半导体激光单模光纤和相位板衍射准直技术结合起来,利用面阵CCD采集图像,通过测量光斑的位移变化确定平面镜和光栅的角度变化.实验表明.该方法可以测量掠入射情况下单色仪联动时的转角重复精度,测量精度可达士0.1",此测量精度优于同等实验条件下的商用ELCOMAT 3000自准直仪的测量精度.     

多功能夫琅禾费衍射演示仪的研制

针对目前国内夫琅禾费衍射演示仪存在的问题,研制了一种＂多功能夫琅禾费衍射演示仪＂,实现了26种衍射缝的夫琅禾费衍射的演示实验及相应的计算机（变参数）模拟仿真实验,具有演示与仿真一体化、演示种类多、演示效果明显,自动快速、使用方便、功能多样等特点,能够满足光学课程对夫琅禾费衍射进行演示实验的要求。     

螺旋型波带片聚焦特性研究

提出了一种计算螺旋型波带片聚焦特性的方法。从衍射积分理论出发对螺旋型波带片的聚集特性进行了理论计算,推导出了级数形式的解析解,获得了螺旋型波带片"空心"焦点的场强分布。利用螺旋型波带片的聚焦特性,对其成像进行了数值模拟和理论分析。理论分析表明螺旋型波带片的空间分辨率与其"空心"焦点的环宽有关。通过验证实验证明理论分析与实验测试一致,为螺旋型波带片成像理论和模拟计算提供了一种有效手段。     

多圆孔夫琅和费衍射的研究及衍射图样的可视化

为了认识多圆孔衍射的物理特征和图样特点,通过多圆孔衍射与光栅衍射的类比,结合单个圆孔的衍射和光栅的多条缝之间的干涉,得出多圆孔夫琅和费衍射的光强公式。采用MATLAB语言编程作图,得到多圆孔夫琅和费衍射图样,并方便地观察衍射图样随各个参数的变化,有助于学生更好地理解干涉和衍射现象的物理本质。计算机可视化光学现象,有助于提高学生的学习兴趣。圆孔衍射与多缝干涉结合起来处理问题的思路,有助于激发学生深入思考,进行探究式学习,培养创新能力。     

互补Sierpinski地毯光栅夫琅和费衍射现象的研究

利用菲涅耳 基尔霍夫光栅衍射原理和傅里叶分析方法，对具有分形结构互补Sierpinski地毯光栅的夫琅和费衍射现象进行了探讨。导出了观察平面上的频谱函数、振幅函数以及光强函数。运用MATLAB软件对该光栅的衍射现象进行了仿真，并绘制出其幅 频特性曲线。结果表明，在各阶光栅的衍射图样中，幅度较大的部分主要集中在接收屏的中心区域，而在偏离中心的区域内，幅度值较小，在较远区域幅度值趋近于零，这说明获得的衍射图样不仅具有衍射光的基本特性，而且都呈现出明显的分形特征。     

夫琅禾费单缝衍射实验的仿真研究

根据夫琅禾费单缝衍射理论,应用MATLAB软件编程,对衍射过程进行仿真,作出单缝衍射光强分布图形,通过改变光的波长、入射方向、缝宽和焦距,观察到单缝衍射光强分布的变化规律.     

Suppression of Sidelobe for Acousto-Optic Tunable Filter in Near-Infrared Spectral Monitoring

. In this paper we calculated the acoustic intensity distribution of different transducers, and designed acousto-optic tunable filter(AOTF) based on different transducers. Through the experiment, we find sidelobe can be reduced by changing the transducer geometry.     

夫琅和费衍射颗粒粒度测量中的改进Chin-Shifrin反演算法

在基于线阵CCD的夫琅和费衍射颗粒粒度测量中,采用Chin-Shifrin积分变换反演算法使得反演的粒度分布出现假峰现象.为解决此问题,提出在该Chin-Shifrin积分变换反演算法中引入矩形窗函数,并在分析颗粒粒径与衍射光强导数最小值之间关系的基础上,确定矩形窗函数中心点位置及左右边界,利用该矩形窗函数对粒度分布进行截断处理,消除虚假峰,提高反演颗粒粒度分布的准确性.分别对两种标准颗粒进行了测量,并对不同算法的反演结果进行了对比.实验结果表明:引入矩形窗函数的改进Chin-Shifrin算法,能够有效排除粒度分布中的多假峰;粒度分布测量相对误差小于3%,重复性小于4%.     

Suppression of Multiple-Beam Interference Noise in Testing an Optical-Parallel Plate by Wavelength-Scanning Interferometry

Measurements of optical parallel plates in a Fizeau interferometer lead to problems from multiple-beam interference noise unless the back surface of the plate has an additional treatment to prevent its reflection from reaching the detector. Such internal-reflection noise can be separated from the fundamental interference signal by its modulation frequency in a wavelength-scanning interferometer. However, to completely eliminate the noise, the air-gap distance between the testing and reference surfaces of the interferometer must be adjusted to a specific value, depending on the thickness and refractive index of the plate. This adjustment requires an undesirable change in the air gap, which is related to the phase modulation rate of the interferometer, and also requires additional information regarding the testing plate, which makes the measurement laborious. We show that if we add new symmetries to the sampling functions of the phase measuring algorithm, we can obtain significantly greater tolerance for the air-gap error. A new 19-sample algorithm allows a tolerance of ±23% while keeping the systematic errors at less than λ/200. The periodicity of the new algorithm and an integrating bucket technique also provide more options for the thickness of the testing plate, which guarantees an air-gap distance more independent of this thickness.     

Modeling of Multiple Scattering Effects in Fraunhofer Diffraction Particle Size Analysis

A model for the direct problem of calculating the forward scattering signature of a multiple scattering medium is presented. The new formulation is optimized for integration into schemes for reconstructing the particle size distribution from laser diffraction (forward scattering) signatures obtained from optically thick media. The analysis is valid for media where the particle sizes and interparticle spacings are large (relative to the wavelength and the particle size, respectively) such that Fraunhofer diffraction theory adequately describes the properties of the forward scattered light from individual scattering events. The simulated performance of laser diffraction particle sizing instruments was then studied using predictions of the scattered light signatures which would be measured by laser diffraction instrument under multiple scattering conditions. The results were compared with experimental data and theoretical calculations based on other models.     

局部激励法产生靶波来消除螺旋波

提出采用局部激励方法产生靶波来消除抑制激发介质中的漂移(和稳定的)螺旋波．通过在系统中任意选择一个格点进行采样，将采样格点信号反馈到系统局部区域可产生一个稳定的靶波．数值计算表明：该方法可以消除均匀和非均匀介质(扩散系数随时间或空间变化)中的螺旋波(稳定旋转的螺旋波和漂移的螺旋波)，并且对于时空噪声具有一定的抗干扰性．     

用于同步辐射光源的成像板粉末衍射系统

报道了我们研制的一套成像板粉末衍射装置,对其误差来源进行了详细的分析讨论,并与衍射仪进行了比较.该装置的半径为143.3mm,最大测量角度范围不160°，最大角度(2q )偏差小于0.03°,这些性能指标已被实验所证实,完全可应用于粉末衍射全谱的测量.     

Fraunhofer Diffraction Pattern by a Slit Aperture between a Knife Edge and a Metal Cylinder

The Fraunhofer diffraction pattern of an aperture formed between a knife edge and a smooth surface of a turned metal cylinder or half cylinder is different from the diffraction pattern of an ideal slit aperture. The diffraction pattern is simulated by adding the light reflected by the cylinder surface to the pattern formed by a slit, and is measured using a cylinder that has been partly cut away so that it can represent either a full or half cylinder. The theoretical and measured patterns agree well with each other.     

Mitigation of Diffraction Fringe in Quasi-Far Field Pattern Using an Edge-Shaped Plate

A new concept is developed for improving the laser intensity distribution in quasi-far field using geometrical optics of a continuous phase (so-called edge-shaped plate). The diffraction fringe on a quasi-far field beam pattern of a well collimated He-Ne laser beam 5 cm in diameter is mitigated by the insertion of an edge-shaped plate with a super-Gaussian (n=40) surface profile. A diffraction code using Fresnel-Kirchhoff diffraction integration was developed to calculate diffraction patterns of aspherical optical elements. The measured beam profile is in good agreement with the calculated beam pattern.     

圆屏(球)和圆环菲涅耳衍射的解析表达式

在标量衍射理论的基础上，给出了圆屏（球）和圆环菲涅耳衍射的振幅及光强解极表达式。计算了光强分布曲线，并将计算实例和有关资料中的实验与计算结果进行了比较。同时指出所谓无衍射光束实际上是一种菲涅耳衍射现象。     

Diffraction Properties for 1000 Line/mm Free-Standing Quantum-Dot-Array Diffraction Grating Fabricated by Focused Ion Beam

In the research of inertial confinement fusion （ICF）, diagnosis of soft x-ray spectra radiated from pellet implosion is a crucial approach to compre- hend the space-time characteristic of plasma and the laser-plasma interactions. Conventional black- white transmission grating （TG） as a speetrophotom- etry element has been widely used in the region of op- tical measurements. However, the inherent high-order diffraction of black-white TG can overlap the informa- tion from the first order diffraction. The uncertainty of unfolding the complex process is the main diffi- culty in precise spectral analysis, which greatly hin- ders being able to stripe out the reasonably physical information. Quantum-dot-array diffraction grat- ing （QDADG） proposed by Cao, where the trans- mittance distribution obeys the sine form exactly, is an ideal amplitude TG and has perfect properties of pro- ducing just one pair of conjugate first order diffraction lines and suppressing the high order diffraction.The traditional fabrication technique for QDADG is the electron beam lithography （EBL） and the x-ray lithog- raphy （XRL）. Owing to its capability of gen- erating patterns and the high resolution, EBL plays an increasingly important role in the micromachining, and is recognized as the main approach of fabricating a mask. The fabrication of nanoscale patterns with steep cross section is the superiority of XRL, which possesses the advantages of high efficiency, nanoscale resolution and great penetration capability. On the basis of the above-mentioned processing technique, 1000 line/mm quasi-sinusoidal single-order diffraction TG with the minimal feature structure of 500 nm was reported by Kuang et al., and can be applied in the ICF research. For single order diffraction grating, unfortunately, the promotion and application of EBL and XRL are restricted by the complex process, long period, difficult manufacture and the existence of the supporting film that absorbs x-rays and distorts the light information.     

超短脉冲激光光束被局域体全息光栅衍射的性质分析

利用二维耦合波理论,分析了超短脉冲激光光束被完全重叠型的局域体全息光栅衍射的时空变化性质,给出了衍射和透射脉冲激光光束沿光栅出射边界的强度时空分布。以LiNbO3晶体为例,数值研究了衍射光脉冲强度沿光栅出射边界的分布和脉冲波形的变化及光栅的总衍射效率受光栅二维尺寸、入射角度、光栅折射率调制度及入射脉冲的脉冲时域半峰全宽等条件的影响而变化的情况。与一维体全息光栅对超短脉冲激光光束衍射的性质,及此光栅对连续光衍射的性质作比较,给出了合理选择光栅参量及入射条件以在光栅出射边界上得到总衍射效率较大且分布较均匀的衍射光脉冲的方法。     

基于MATLAB的简单孔形夫琅禾费衍射实验的计算机模拟

1引言 　　衍射是光波的重要特征之一,夫琅禾费衍射在实际应用和理论上都很重要.这类衍射的分析和计算都比较简单,一般通过数值计算就能得到衍射的光强分布.对简单孔径衍射的模拟计算已经有过研究,但无一例外是采用数值计算的方法,其实我们从图像变换的角度出发同样可以得到相同的结果,利用MATLAB语言做这项工作将变得非常容易.MATLAB功能强大、简单易学、编程效率高而被广泛地应用在工程计算、数值分析和图像处理等领域,对于光学实验的模拟是非常方便和灵活的.……