Non-uniformities in Thick Dichromated Gelatin Transmission Gratings

Abstract

The angular characteristics of transmission gratings are studied for the case when three parameters, namely the dielectric-constant modulation, the average dielectric constant and the grating vector vary with distance in the grating. The diffraction efficiency is worked out with the aid of a coupled-wave theory for linear and quadratic variation of the parameters. Gratings recorded in thick (≈ 60 µm) dichromated gelatin plates are measured. The spatial variations of the parameters are deduced by comparing the experimental and theoretical results.     

Dichromated Gelatin Reflection Gratings

Abstract

Reflection gratings were recorded in dichromated gelatin by using a non-symmetrical recording geometry. In addition to the primary grating, secondary gratings were also formed, as is generally known. It is found that the secondary gratings assist the structure stability during development in the exposure energy range (50–100) mJ cm^?2. The structure containing these secondary gratings is more rigid than those without and the reflection grating period is more stable during the development process in this exposure energy range, which is most suitable for the transmission grating formation. Secondary gratings also cause unwanted noise, but the noise level is low and the improved stability outweighs the extra noise.     

Reprocessibility of Dichromated Gelatin Reflection Gratings

Abstract

The reprocessibility of dichromated gelatin reflection gratings is studied. Reflection gratings developed in six slightly different ways are reprocessed after three years storage. Reflection (diffraction) efficiencies are strongly decreased during storage. After reprocessing reflection efficiencies are close to the original reflection efficiencies. Restoration is better when the original reflection efficiency (RE) is not very high (RE <90%). When, the plates, which are rapidly dehydrated during development procedure, are reprocessed using slow dehydration, reflection efficiencies have often been even better after reprocessing than one day after exposure and the original development procedure.     

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.     

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...     

Secondary Holograms in Dichromated Gelatin Filters

Reflective volume gratings in dichromated gelatin film have been studied under conditions in which secondary holograms are produced, where, during exposure, the holographic film is placed in optical contact with a prism. Optimum reconstruction angles and diffraction efficiencies are determined for the secondary holograms that are recorded as a result of internal reflection.     

Bandwidth in Dichromated Gelatin Holographic Filters

Refractive volume gratings in dichromated gelatin film have been studied. The swelling of the emulsion during developing leads to displacement of the interference fringes from the positions observed for the exposure set-up and the fringes are smoothly curved rather than irregular. The effects of the displacement are studied in exposed and developed holograms by examining the reconstruction angle and spectral bandwidth when using white light reconstruction. The influence of construction geometry and absorption on spectral bandwidth is illustrated with experimental results.     

Holographic Optical Beam Splitters in Dichromated Gelatin

Abstract

Holographic beam splitters can split an incoming beam into several partial beams travelling at different angles with arbitrary intensities, thus offering high design flexibility. In this paper the fabrication of beam splitters as multiplex holograms in dichromated gelatin is reported. Shrinking or swelling of the gelatin was avoided by careful process control, reciprocity law failure (as expected from silver halide holograms) was not observed, and, for example, a 1 : 2 beam splitter diffracting 47·4% and 47·0% of the incoming light into two higher orders was realized.     

Influence of Raw Material and Processes of Gelatins upon Photographic Characteristics of Dichromated Gelatin

Carbon tissues prepared using types of gelatin differing in raw material and process were sensitized by dichromate and their photographic characteristics were investigated. Sensitivity and gamma were dominantly determined by the higher molecular weight components of the gelatin, sharpness and resolving power were dominantly determined by viscosity; these properties were little affected by its origin.     

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.     

Diffraction Efficiency of Binary Metal Gratings Working in Total Internal Reflection

Experimental and theoretical investigations on the diffraction efficiency of binary metal gratings working in total internal reflection are carried out. Using the method of amplitude transmission an expression that describes the efficiency of high diffraction orders is derived. Equations for the gratings' diffraction efficiency in the form of infinite series are obtained by the convolution method. It is demonstrated that both approaches yield one and the same result. The theoretical results are compared with the experimental data on the diffraction efficiency dependence on the angle of incidence and duty factor. Qualitatively, the theory describes satisfactorily the behaviour of the experimental relationships. A deviation is observed in the even orders and in the vicinity of the critical angle.     

无明胶重铬酸盐全息图的后处理方法

本文介绍了无明胶重铬酸盐全息记录软片(简称NGD)的感光成像机理。实验研究了NGD全息图的后处理过程对衍射效率和表面灰雾的影响,给出了处理时间与衍射效率,表面灰雾的关系曲线,提出了一种适用于这种新材料后处理的方法。     

WDM与OTDR结合的弱光栅分布式温度传感网络

提出一种基于弱反射布拉格光栅的新型分布式温度传感网络,将WDM与OTDR相结合,采用WDM技术提高光栅的复用容量,利用OTDR对各个弱光栅进行实时检测,以实现光栅的密集串行复用,并提高空间分辨率。使用可调谐脉冲激光为光源,多组不同中心波长弱光栅等间距刻制在一根光纤上。利用一根光纤刻制的三组反射率为3%,中心波长分别为1544.660nm、1545.802nm和1546.900nm的9个FBG进行了温度实验。实验结果表明,在5～80℃的温度范围内,FBG的中心波长随温度变化呈良好的线性,线性度达到99.6%以上,温度测量的分辨率最高达到0.11℃,空间分辨率可达2m。     

Thermal Transitions in Gelatin and Aqueous Gelatin Solutions

On the basis of the characteristic enthalpy changes associated with glass transformation, the glass transition (T_g) in gelatin can be detected readily, in addition to the helix-to-coiltransition, by difTerential scanning calorimetry, and the effects of water content on these transitions can be measured directly. The thermal behaviour of aqueous, deionized bone-gelatin systems with up to about 20 wt";' water is typical of amorphous or partially amorphous polymer-diluent systems depending upon the amount of gelatin structural order developed. Extrapolations of the T_g data to the T_g reported for water and of the helix-to-coiltransition data to that reported for aqueous gelatin solutions containing 90 wt% water are reasonable. Further, the T_g data suggest that the equilibrium water contents of aqueous gelatin systems containing gelatin structural order are higher than those of structureless systems at corresponding relative humidities.     

无明胶重铬酸盐全息记录软片的正性光抗蚀特性

对无明胶重铬酸盐全息记录软片（ＮＧＤ）的光正性抗蚀特性进行了分析研究，通过对溶解度的分析及红外光谱的测定，首次提出ＮＧＤ是一种新型的紫外正性光抗蚀材科，给出了实验及分析结果。     

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.