全息离子束刻蚀衍射光栅

全息离子束刻蚀衍射光栅集中了机械刻划光栅的高效率和全息光栅的无鬼线、低杂散光、高信噪比的优点．全息离子束刻蚀已作为常规工艺手段应用于真空紫外及软x射线衍射光栅的制作．文章对全息离子束刻蚀衍射光栅的制作方法、主要类型、研究现状和应用进行了综述．     

Holographic diffraction gratings with multilayer insulator coatings

Based on numerical modeling of metallized diffraction gratings with multilayer insulator coatings, the diffraction efficiency of such gratings is investigated, assuming that the initial profile of the metallized grat-ing is not reproduced in the course of sequential deposition of coating layers. From comparison of experimental and calculated data, it is concluded that the initial grating relief is subject to considerable smoothing. The new nontraditional range of the optimum values of layer thicknesses, which provides a high diffraction efficiency in the operating wavelength range of 1.06 μm, is suggested. The stability of the diffraction efficiency with respect to random errors in the thickness of insulator layers deposited is investigated numerically.     

Holographic diffraction gratings using polymer-dispersed ferroelectric liquid crystals

By controlling the morphology of holographic polymer-dispersed ferroelectric liquid crystals (FLCs), highly aligned FLC domains are obtained for diffractive optical applications. Rapid, thresholdless switching is observed for various grating pitch sizes between approximately 3 and approximately 12 microm. A simple phenomenological model is presented encompassing a distribution of domain sizes and an effective field that stabilizes the FLC domains to reflect the observed thresholdless switching and optical behavior.     

一种用于制作数字合成全息图的光学全息元件

介绍了两种新型的应用于数字合成全息图的光学全息元件——全息柱面镜的制作原理及方法,并研究了其性能情况,表明全息柱面镜可以将光散射在焦平面上并且不会破坏图像的平面特征,可以有效改进图像质量提高光能利用率。     

Holographic optical element for laser time-of-flight flow sensor

A novel laser time-of-flight flow sensor has been developed. A specially designed holographic optical element (HOE) constitutes the basis of the optical front end of the sensor. The multifunctional HOE maintains both the transmitting and receiving functions of the optical front end and is designed so that the alignment of the optical system is independent of small changes in the wavelength and temperature. This makes it possible to use a laser diode and makes the optical front end very compact and robust. The HOE is produced as a high-efficiency surface relief grating, thus making a large-scale production through polymer replication possible. The design and fabrication of the HOE is described and the stability of the sensor system is discussed with respect to wavelength variations. Direct calibration measurements on the sensor and test velocity measurements are presented. The sensor is intended for water flow measurements in pipes and can also be used for velocity measurements of solid surfaces.     

Holographic storage of information and peculiarities of light diffraction in birefringent electro-optic crystals

Using birefringent crystals such as LiNbO₃: Fe, reading and writing of holograms at different wavelengths and so nondestructive readout of information may be accomplished.     

Binary diffraction optical element focusing a Gaussian beam to a longitudinal segment

A phase binary ring diffraction optical element (DOE) with a radius of 3.5 mm and microrelief height of 1.06 μm was calculated and fabricated. The element focuses a Gaussian beam of a He-Ne laser with radius of 1.5 mm to a 1.7 mm long axial segment, which ranges from 51.9 to 53.6 mm, with a focal spot diameter of about 30 μm.     

Switchable optical element with Bragg mode diffraction

A theoretical model of a new electronically switchable grating design that uses a multilayer structure of an electro-optic (EO) material with an interdigitated-electrode type of array is proposed as an original technique for calculating the induced refractive index. It is shown that asymmetrical distribution of the electric field induces a slanted Bragg grating, which allows the slant angle to be switched electronically among more than two switching states. Parameters of the suggested design are calculated for a number of EO materials. A special case of frequency-based switching is anticipated for some polymer-dispersed liquid-crystal materials.     

Holographic prism as a new optical element: I. Principle of operation and experimental implementation

Optics and Spectroscopy - A new multivalued measure of plane angles is proposed, which is based on a highly stable system of superimposed holograms recorded in a photochromic material. Their mutual...     

电光型衍射元件在光学成像系统中的应用

本文介绍一种以液晶空间光调制器作为调制位相信息的衍射元件,获得可变焦长的菲涅耳透镜,以及该元件在光学成像系统中的应用。     

Correlation between element concentrations and x-ray diffraction patterns in hair

A correlation between the character of x-ray patterns and the element composition of human hair was found. X-ray diffraction and fluorescence analysis of human hair were carried out using synchrotron radiation of the storage ring of the Institute of Nuclear Physics, SB RAS. Some factors leading to the appearance of the diffuse ring in keratin fibrils, which corresponds to a molar periodicity of 4.44 nm, were shown, as was the ring's connection with the element composition of hair. The role of metals in the matrix complex was considered. Copyright © 2002 John Wiley & Sons, Ltd.     

X-ray diffraction characterization of a spatially coherent crystalline nanocomposite obtained from a melt of KCl, KBr and KI salts

Crystalline bulks, obtained by the Bridgman technique from a melt that was previously prepared by mixing equal molar fractions of the salts KBr, KCl and KI were characterized by powder and single-plate X-ray diffraction. The crystalline bulks are formed by a composite material consisting of a highly textured aggregation of crystallites of two different face-centred-cubic solid solutions with corresponding unit-cell sizes of 7.020(2) and 6.456(3) Å. The relative molar fraction concentrations of these solid solutions in the composite are about 0.348 and 0.652, respectively. From these solutions, the first is identified as the binary KBr(9.7%):KI(90.3%) mixed phase and the second is discussed to be the ternary KBr (45.9%):KCl (51.1%):KI (3.0%) mixed phase. The lattices of most of the crystallites forming the composite, no matter the phase they belong to, are spatially coherent to each other within the crystalline bulk.     

Holographic prism as a new optical element: II. Method of measurement of reproducible angles

To determine the precise values of angles stored and reproduced by a new multivalued measure of plane angles, i.e., a holographic prism, it is expedient to use a procedure for collating two circular scales, one of which is determined by the prism upon its rotation on a rotary table, while the other is the device’s own scale. The two scales are considered to be equivalent. The collation procedure is discussed taking into account target (deviations of sought values of angles of both scales from their nominal values) and a number of nuisance parameters of the procedure. The scheme of the collation device is considered. The geometric model that determines sources of errors caused by design features of signal reading and recording devices of the holographic prism is analyzed.     

The investigation of three layers diffraction optical element with wide field of view and high diffraction efficiency

In this paper, a novel three layers diffraction optical element (TLDOE) composed of the optical materials with different indices and dispersion in each layer has been designed and investigated, the principle of selecting optical materials is discussed as well. The diffraction efficiency of the TLDOE at each wavelength in designed band is larger than 90% and the field of view (FOV) can even reach 110°, which can effectively improve energy utilization ratio and image quality of the hybrid refractive–diffractive optical system.     

超声TOFD检测的有限元分析及其试验验证

超声衍射时差法（Ultrasonic TOFD）通过接收衍射波信号对缺陷进行测深定高,分析超声波在检测对象中的传播对于提高检测效力具有重要作用。本研究采用有限元方法模拟超声TOFD检测过程,探讨了缺陷衍射波的产生及传播特性,并通过试验对模型结果进行了验证。研究表明：有限元建模能够直观显示超声TOFD检测的声波传播过程,模拟结果与试验具有较好的一致性;实际检测过程中涉及的要素,如：探头优化布置、衍射波传播方式、幅度分布、缺陷端部形状对衍射过程的影响均能较好地体现在仿真模型中;超声TOFD检测的有限元模型可实现检测过程可视化,并可为工程检测人员提供一种新的检测方案设计和结果分析的手段。     

Toward a Mathematical Holographic Principle

In work started in [17] and continued in this paper our objective is to study selectors of multivalued functions which have interesting dynamical properties, such as possessing absolutely continuous invariant measures. We specify the graph of a multivalued function by means of lower and upper boundary maps \(\tau _{1}\) and \(\tau _{2}.\) On these boundary maps we define a position dependent random map \(R_{p}=\{\tau _{1},\tau _{2};p,1-p\},\) which, at each time step, moves the point \(x\) to \(\tau _{1}(x)\) with probability \(p(x)\) and to \(\tau _{2}(x)\) with probability \(1-p(x)\) . Under general conditions, for each choice of \(p\) , \(R_{p}\) possesses an absolutely continuous invariant measure with invariant density \(f_{p}.\) Let \(\varvec{\tau }\) be a selector which has invariant density function \(f.\) One of our objectives is to study conditions under which \(p(x)\) exists such that \(R_{p}\) has \(f\) as its invariant density function. When this is the case, the long term statistical dynamical behavior of a selector can be represented by the long term statistical behavior of a random map on the boundaries of \(G.\) We refer to such a result as a mathematical holographic principle. We present examples and study the relationship between the invariant densities attainable by classes of selectors and the random maps based on the boundaries and show that, under certain conditions, the extreme points of the invariant densities for selectors are achieved by bang-bang random maps, that is, random maps for which \(p(x)\in \{0,1\}.\)      

Holographic formation of dynamic transmission diffraction gratings in a photopolymer material in the process of two-beam interaction at low contrasts

In the present study, the process of formation of holographic transmission diffraction gratings in photopolymer media is investigated at low contrasts with allowance for self-diffraction of recording waves. A theoretical model for the first spatial harmonics of the refractive index grating is constructed based on a solution of the coupled kinetic photopolymerization and diffraction equations. The temporal dynamics of amplitude and phase spatial profiles of harmonics, diffraction efficiency, and angular selectivity of recorded gratings is theoretically investigated. The calculated and experimental data are compared. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 35–42, November, 2006.     

Triple Encrypted Holographic Storage and Digital Holographic System

We propose a triple encrypted holographic memory containing a digital holographic system. The original image is encrypted using double random phase encryption and stored in a LiNbO3：Fe crystal with shift-multiplexing. Both the reference beams of the memory and the digital holographic system are random phase encoded. We theoretically and experimentally demonstrate the encryption and decryption of multiple images and the results show high quality and good fault tolerance. The total key length of this system is larger than 4.7×10^33.