Diffraction management

By using the diffraction properties of waveguide arrays, we propose a scheme to produce structures with designed diffraction. We fabricated arrays with reduced, canceled, and even reversed diffraction. Results of experiments with such waveguides are presented and compared with the predictions made by coupled-mode theory.     

点衍射干涉仪中小孔衍射波面误差分析

针孔或光纤直径的大小是影响点衍射干涉仪检测精度的重要因素,在实际检测中须根据检测任务的精度要求来选择小孔的尺寸.基于标量衍射理论,仿真计算了小孔尺寸引起的衍射波面相对标准球面偏离的误差.结果表明,当小孔直径为2.5μm,数值孔径(NA)为0.3时,与小孔有关的光学系统误差峰值(PV)约为0.07 nm.仿真方法和计算结果为针对各种高精度面形检测任务而设计点衍射干涉仪和分析其精度提供了理论和数据参考.     

N-Slit Diffraction Pattern

The diffraction pattern for particles passingthrough N slits is obtained by a truncation assumptionon the Gaussian wave function when passing the slits andby pure wave propagation governed by the Schrodinger equation with boundaries. The standard limitingsituations give the usual results. In case of a greatnumber of equal and equally separated slits thecalculations are performed by considering also theenergy band structure induced by the periodic boundarygeometry on the initial conditions. The results, whichare qualitatively satisfactory in both cases, do notagree completely in general nor in the limiting cases.     

Diffraction at backangles

The backangle differential cross section is analyzed using an improved analytical approach. The differential cross section smoothed over the frequent angular oscillations is shown to be an oscillating function of the energy in the backangle region. Analogy with the radar scattering of light is pointed out. Angular and energy amplitude functions are introduced and discussed on the basis of general arguments and some simple examples.     

Diffraction theory of quasicrystals

The diffraction problem of quasicrystals is solved with the aid of shift operators, s _q(x, y, z) (q = x, y, z). Starting from certain sets of latent lattices which have to be optimized according to chemical composition, density, and diffraction pictures, it is shown that periodic structures are determined by as many parameters as the number of independent positions. Furthermore, the Fourier coefficients (Fc's) are strictly periodic. Structure factors are given by sums of products of Bessel functions (Bfs). The amplitudes of Fc's enter the arguments of Bf's, while their phases determine phase factors. The diffraction pictures show periodic properties, as far as the orders of Bf's and Fc's are concerned. This periodicity is violated only by the arguments of Bf's. Hence direct calculation of phases of reflections with certain ambiguities is possible. Quasicrystals are characterized by incommensurate modulations with an infinite number of possible Fc's which can not be derived from diffraction patterns. This difficulty is overcome by the observation of extinction rules, limiting the number of reflections observed. The orders of Fc's, Bf's respectively, entering the sum mentioned above, are correlated by convolution properties in diffraction. Taking into account their periodicities and the existence of sets of latent lattices, regularities in the diffraction pattern result which are briefly discussed.     

Diffraction in three dimensions

Atmospheric Convection . By K. A. Emanuel. 1994, £47.50 (hbk), pp. x+580. Oxford, ISBN 0 19 506630 8. Scope: text. Level: postgraduate.

Automotive Sensors . By M. H. Westbrook and J. D. Turner. 1994, £75.00, US$149.00 (hbk), pp. xviii + 253. IOP, ISBN 0 7903 0293 3. Scope: monograph. Level: specialist.

Computation in Modem Physics . By W. R. Gibbs. 1994, £38.00 (hbk), pp. xvii + 348. World Scientific, ISBN 981 02 2044 8. Scope: text. Level: undergraduate and postgraduate.

Electron Correlations in Molecules and Solids , 2nd Edn. By P. Fulde. 1993, DM78.00 (pbk), pp. xiv + 422. Springer-Verlag, ISBN 3 540 56376 8. Scope: monograph. Level: postgraduate and specialist.

Field Theory, A Path Integral Approach . By A. Das. 1994, £48.00 (hbk), pp. xv + 399. World Scientific, ISBN 981 02 1396 4. Scope: lecture notes. Level: postgraduate.

Infrared Technology Fundamentals , 2nd Edn, revised and expanded. By M. Schlessinger. 1994, US$125.00 (hbk), pp. xii + 462. Dekker, ISBN 0 8247 9259 9. Scope: monograph. Level: postgraduate and specialist.

Oceanography and Acoustics . Edited by A. R. Robinson and D. Lee. 1994, US$65.00 (hbk), pp. xvii + 257. AIP, ISBN 1 56396 203 9. Scope: multi-author review. Level: postgraduate and specialist.

Optoelectronic Integration: Physics, Technology and Applications . Edited by O. Wada. 1994, Dfl. 275.00, US$130.00, £96.25 (hbk), pp. x + 458. Kluwer, ISBN 0 7923 9453 4. Scope: multi-author review. Level: postgraduate and specialist.

Photonic Devices and Systems . Edited by R. C. Hunsperger. 1994, US$135.00 (hbk), pp. xi + 426. Dekker, ISBN 0 8247 9243 2. Scope: multi-author review. Level: postgraduate and specialist.

Physics and Our View of the World . Edited by J. Hilgevoord. 1994, US$22.95 (pbk), pp. 304. Cambridge, ISBN 0 521 47680 1. Scope: multi-author review. Level: scientists and philosophers of science.

Polymer Physics . By U.W. Gedde. 1995, £49.00 (hbk), £24.99 (pbk), pp. x + 298. Chapman &; Hall, ISBN 0 412 62640. Scope: textbook. Level: undergraduate and postgraduate.

Quantization of Gauge Systems . By M. Henneaux and C. Teitelboim. 1994, US$29.95, £25.00 (pbk) pp. xxii + 520. Princeton, ISBN 0 691 03769 8. Scope: textbook. Level: postgraduate and specialist.

Semiconductor Raman Lasers . By K. Suto and J.-I. Nlshlzawa. 1994, £63.00 (hbk), pp. ix + 226. Artech, ISBN 0 89006 667 1. Scope: monograph. Level: specialist.

Shapes and Shells in Nuclear Structure . By S. G. Nilsson and I. Ragnarsson. 1995, £60.00, US$89.95 (hbk), pp. xiv + 408. Cambridge, ISBN 0 521 37377 8. Scope: textbook. Level: postgraduate.

Supersymmetric Gauge Field Theory and String Theory . By D. Bailin and A. Love. 1994, £80.00, US$160.00 (hbk), £27.50, US$49.00 (pbk), pp. xii + 332. IOP, ISBN 0 7503 0268 2. Scope: textbook. Level: postgraduate.

Short notices Advanced Series in Neuroscience , Vol. 3. Biology and Computation, A Physicist's Choice. Reprint volume. Edited by H. Gutfreund and G. Toulouse. 1994, £94.00 (hbk) pp. xv + 852. World Scientific, ISBN 981 02 1405 7. Scope: reprints. Level: postgraduate and specialist.

Electronic Structure of Refractory Carbides and Nitrides . Edited by V. A. Gubanov, A.L. Ivanovsky and V. P. Zhukov. 1994, $79.95 (hbk) pp. xiv + 256. Cambridge University Press, ISBN 0 521 41885 2. Scope: monograph. Level: postgraduate and specialist.

Fritz London: A Scientific Biography . By K. Gavroglu. 1995, £50.00 (hbk), pp. xxiv + 299. Cambridge University Press, ISBN 0 521 43273 1. Scope: biography. Level: general reader.

Gallium Arsenide and Related Compounds 1993 . Edited by H. S. Rupprecht and G. Weinmann. 1994, £115.00, US$230.00 (hbk), pp. xxiv + 842. IOP, ISBN 0 7503 0295 X. Scope: conference proceedings. Level: postgraduate and specialist.

Matvei Petrovich Bronstein and Soviet Physics in the Thirties . By G. E. Gorelik and V. Y. Frenkel. 1994, £65.00, DM 168.00. sFr. 148.00 (hbk), pp. 208. Birkhauser, ISBN 3 7643 2752 9. Scope: biography. Level: non-specialist.

Physical Chemistry . 5th edn. By P. W. Atkins. 1994, £24.00 (pbk), pp. xix + 1145. Oxford, ISBN 0 19 855730 2. Scope textbook. Level: undergraduate.

Polyominoes. Puzzles, Patterns, Problems, and Packings . Revised and expanded 2nd edn. By S.W. Golomb. 1994, US$24.95, £19.95 (hbk) pp. xii + 181. Princeton University Press, ISBN 0 691 08573 0. Scope: text. Level: non-specialist.

Supercollider 5 . Edited by P. Hale. 1994, US$195.00 (hbk), pp. xxviii + 970. Plenum, ISBN 0 306 44705 3. Scope: conference proceedings. Level: postgraduate and specialist.

World Scientific Series in 20th Century Physics , Vol. 5. Selected Papers of Abdus Salam (With Commentary). Edited by A. Ali, C. Isham, T. Kibble and Riazuddin. 1994, £64.00 (hbk) pp. xiv + 679. World Scientific, ISBN 981 02 1662 9. Scope: reprinted papers. Level: specialist.     

Spectral Theory of Diffraction

In this paper we present an overview of the spectral domain approach for solving a variety of high frequency diffraction problems. We demonstrate via a number of examples that the fields derived from the use of the Spectral Theory of Diffraction (STD) remain uniformly valid for all observation angles, including the shadow boundary, the reflection boundary and the caustic direction where the conventional Geometrical Theory of Diffraction (GTD) breaks down. Furthermore, we show how the accuracy of STD can be improved and its range extended by combining it with integral equation methods in the spectral domain. This work was supported in part by U.S. Army Research Grant DAHC04-74-G0113 and in part by Office of Naval Research Grant N00014-75-C-0293.     

Diffraction structural biology--introductory overview

An introductory overview to the special issue papers on diffraction structural biology in this issue of the journal.     

Basics of X-ray Diffraction

X-ray diffraction (XRD) is the most comprehensive tool to identify minerals in complex mineral assemblages. The method is briefly described with special emphasis on clay and ceramics. As an example, an investigation of graphite-containing pottery sherds by XRD is presented. By comparing the measured XRD data with the patterns simulated by the Rietveld method, the graphite content of such samples could be determined.     

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。     

Diffraction of oriented nano-peapods

This paper presents an investigation of the structural properties of oriented A@SWNT peapods, where A represents any molecular species organized on a 1D cristalline chain inside the single wall nanotubes (SWNT). This study is based on the use of diffraction methods applied to the case of oriented A@SWNT samples. Two preferential orientations of tubes are considered, 1D (fiber) and 2D (pellet) both having an axial symmetry. We show that even in the case of samples presenting a very large mosaic, information about the correlation state between C₆₀ chains and about the C₆₀ polymerization, can be obtained provided that pertinent scans are performed. These are longitudinal scans along and perpendicularly to the symmetry axis accompanied by convenient constant Q scans. Detailed diffraction patterns are simulated in the case of a 2D oriented sample of C₆₀@SWNT peapods (`bucky paper').     

衍射光学透镜的设计

介绍一种衍射光学透镜的通用设计方法，它适用于大的相对孔径和任意的物像共轭距离，同时考虑了透镜基板厚度的影响．设计的结果，用激光写入法加工成透镜，其成像质量达到衍射极限．     

Diffraction of bending waves

This paper is a discussion of the theory of diffraction and scattering of bending waves by mass-impedance loadings of an infinite plane plate. Emphasis is placed on the case of heavy loadings, at which deflexions of the plate are precluded and the scattering is the strongest possible. Examples treated in detail include the diffraction grating, diffraction by a semi-infinite rib, and diffraction by a comb of semi-inifinite ribs.     

微波布拉格衍射实验中测量衍射极大值的新方法

介绍一种在微波布拉格衍射实验中测量模拟晶体衍射极大值的新方法.此方法是采用微波分光仪自动测试系统进行测量,并且利用绘图软件处理数据,可以同时测量简单立方模拟晶体多个晶面的衍射极大值.     

斜入射时光栅衍射特性的理论分析及实验研究

在研究倾斜入射衍射光栅时如何测量光谱波长的基础上,给出了衍射光相对于零级衍射光夹角与倾斜入射光入射角的关系,利用最小衍射角法和等效光栅法测量高压汞灯绿光谱波长,定量分析了在常规衍射光栅实验中斜入射对波长测量结果的影响。