Volume Holographic Gratings: Modelling Their Optical Properties

Abstract

Numerical studies of non-sinusoidal holographic gratings are reported. It is assumed that losses are present during the hologram recording process. At reconstruction the structures are treated as pure-phase volume gratings. The photo induced changes in the refractive index of the material are described by an exponential saturation law. Angular and wavelength selectivities of unslanted transmission and reflection gratings are evaluated.     

Polarization Holographic Gratings

Abstract

The photoinduced anisotropy (dichroism and birefringence) in AgCl emulsions is studied as well as the possibility for chemical fixing of this anistropy. A theoretical relation between the diffraction efficiency of amplitude—phase polarization holographic gratings and the photoanisotropy of the recording medium is derived. Based on this relationship an estimation of the properties of the gratings is presented. Polarization holographic gratings with spatial frequencies of 200 to 2000 mm^?1 and diffraction efficiency up to 1·8% are recorded. The gratings are stable, and do not change in time for more than a year.     

Design of Holographic Gratings

A new approach to the design of holographic concave gratings is presented, in which a grating is treated as if it were composed of many small plane gratings, i.e. of local elementary gratings. A wavefront of the diffracted wave is constructed from the waves diffracted from the local elementary gratings. The expression of the focal curves is represented by the loci of centres of principal curvature of the wavefront. The aberration functions are defined as the differences between the direction cosines of the normal to the diffracted wave and those of the reference spherical wave. Blanks are assumed to be toric. The gratings are designed for use with Seya-Namioka monochromators and grazing incidence monochromators, and their theoretical performances are investigated by means of spot diagrams.     

The Groove Profile Formation of Holographic Gratings

Models for predicting the groove profile of metal coated holographic gratings, fabricated in positive photoresist, are studied. Development is assumed to be an etching process, where the etching is directed perpendicularly to the resist-developer interface. Two methods for metal coating are considered; vacuum evaporation and sputtering, and models that describe the profile formation for these cases are presented. It is noted that even a thin coating has a considerable effect on the profile. The theoretical groove profiles are found to be in good agreement with experimental profiles, obtained from SEM photographs of fabricated gratings.     

Reflection Holographic Gratings for Optical Filtering

From the coupled wave theory the transfer function for phase-reflection holographic gratings is obtained with a view to their application as Fourier filters in the object space. After experimental confirmation, different resonance conditions are presented and suitable approximations are discussed. For resonance at normal incidence, a simplified expression is given for the field complex amplitude transmittance as an explicit function of spatial frequency.     

Multidirectional Holographic Phase Gratings: I. Production and diffraction properties

The production and the diffraction properties of holographically produced multidirectional phase gratings have been discussed. Theoretical interpretations of the experimental results have been outlined. Some practical applications of these gratings have been mentioned.     

High-Frequency Relief-Phase Holographic Gratings on Dichromated Gelatin Processed by Short-Wave UV Radiation

Technical Physics Letters - The possibility of creating relief-phase holographic gratings with high spatial frequency (1500 mm–1) on dichromated gelatin layers processed by destructive effect...     

Holographic Noise Gratings for Analysing and Optimizing Photochemical Processings in Bleached Silver Halide Emulsions

Abstract

Recording noise gratings with single-beam exposures in bleached silver halide emulsions is used as a holographic spectroscopy technique in order to analyse and optimize photochemical processing. In particular, rehalogenating type bleachings are analysed by measuring the transmittance through the recorded and processed holographic plate as a function of the reconstruction angle, the exposure and the concentration of the rehalogenating agent in the bleach bath. The experimental results obtained show us that the analysis of these spurious gratings provides information about the bleaching action during the processing and allows us to identify the optimal concentration of the bleach bath.     

Effect of Temperature Change and Storage Time on Holographic Gratings in KBr Crystals with Colour Centres

Abstract

Holographic gratings have been recorded in additively and electrolytically coloured KBr crystals at wavelengths of 514·5 and 632·8 nm respectively. The storage properties of additively coloured crystals have been investigated for 7 years. It has been proved that the storage times less than 4 years are reasonable. It has also been verified that temperature changes during the recording process are the main reason for low diffraction efficiencies. Finally the influence of the relaxational self-enhancement of the diffraction efficiency on the storage properties of these crystals has been studied.     

The Defocused Image of Sinusoidal Gratings

The defocused image of an infinite sinusoidal grating is calculated by scalar diffraction theory for a perfect optical system. It is shown that the image contrast for both circular and annular pupils and for either incoherent or partially coherent illumination can be found in terms of Incomplete Bessel and Struve functions. The results of some typical cases are given. The effect of limiting a grating to a finite number of periods is considered. The results are applied to a consideration of resolving power tests. L'image défocalisée d'une mire sinusoidale indéfiniment étendue est calculée dans le cadre de la diffraction (avec amplitudes scalaires) pour un instrument stigmatique. On montre que le contraste de l'image pour les pupilles circulaires ou annulaires en éclairage-incohérent ou partiellement cohérent peut être exprimé à l'aide des fonctions de Bessel et de Struve « incomplètes ». On donne les résultats dans quelques cas types. L'effet de la limitation de la mire à un nombre fini de traits est étudié. Des considérations sur les tests de pouvoir séparateur en résultent. Für ein ideales optisches System wird das unscharf eingestellte Bild eines unendlich breiten Sinusgitters aufgrund der skalaren Beugungstheorie berechnet. Es ergibt sich, dass der Bildkontrast für kreisförmige und ringförmige Pupillen und für inkohärente oder teilweise kohärent Beleuchtung mit Hilfe unvollständiger Bessel und Struwefunktionen dargestellt werden können. Für einige typische Fälle werden die Ergebnisse mitgeteilt. Der Einfluss einer Beschränkung auf eine endliche Zahl von Gitterperioden wird geprüft. Die Ergebnisse lassen sich auf die Untersuchung von Auflösungstesten anwenden.     

Zn:Fe:LiNbO3晶体全息存储性能

在ＬｉＮｂＯ３中掺进ＺｎＯ和Ｆｅ２Ｏ３生长了Ｚｎ：Ｆｅ：ＬｉＮｂＯ３晶体。     

Bi12TiO20晶体的全息性能

Ｂｉ１２ＴｉＯ２０晶体是一种优良的全息记录材料。本论文对纯Ｂｉ１２ＴｉＯ２０和掺Ｃｅ∶Ｂｉ１２ＴｉＯ２０晶体的衍射效率、半波电压、旋光度等性能进行了测试，并讨论了掺入的Ｃｅ对晶体性能的影响，Ｃｅ＾４＋离子在晶体中取代Ｂｉ＾３＋离子形成新的区域中心。此外还探讨了Ｔｉ原子对晶体旋光度的影响，认为Ｂｉ１２ＴｉＯ２０晶体旋光度远小于Ｂｉ１２ＳｉＯ２０、Ｂｉ１２ＧｅＯ２０的根本原因在于Ｔｉ原子的性质和极化不     

AgBrI超细粒子乳剂光物理及全息性能的研究

本文研究了三种不同尺寸的AgBrI超细粒子的紫外—可见吸收光谱、低温荧光光谱。实验结果表明,随着颗粒尺寸的减小,吸收峰的位置都发生了规律性的蓝移,表现出量子尺寸效应。激光全息照相的性能测试结果说明：颗粒越细,越有利于提高乳剂的分辨率和衍射效率,以及合适的显影密度也是获得高衍射效率的重要因素。     

A Comparison of the Reflection Properties of Dichromated Gelatin Gratings Developed in Different Ways

Abstract

Dichromated gelatin reflection gratings were developed in six different ways. The maximum of the reflection efficiency and its dependence on the wavelength were measured a day and a year after the development procedure. The differences in results between various development processes were analysed.     

Holographic Beam-splitter in High Luminosity Holographic Recording

A holographic recording method in diffuse light is proposed. This method essentially allows to limit the losses of energy. In addition it is well adapted to the transmission and to the processing of holographic information by means of optic and electronic systems.     

高精度编码器的裂相指示光栅

通过动态莫尔条纹方程,用数学分析的方法,并结合GBJ280等高精度绝对式光电轴角编码器,详细讨论了裂相指示光栅的布局特点,光电信号相位相位补偿原理,以及对编码器精度的影响。