Reflection mode holographic recording in methylene blue-sensitized polyvinyl alcohol acrylamide films

Photopolymer systems can produce good image quality holograms that does not require any post-processing and are environmentally stable with good diffraction efficiency. The present work reports the development of a methylene blue-sensitized polyvinyl alcohol acrylamide (MBPVA/AA) photopolymer system for recording white light reflection holograms. Reflection gratings were recorded in the photopolymer films with different concentrations of methylene blue (MB). Various parameters affecting the holographic properties of the samples were also studied. The holographic performance of the material is found to depend on its chemical composition and the recording parameters.     

Analysis and elimination of boundary reflections in transmission holograms

Elimination of reflections which occur at the glass–air interface of holographic plates is an important factor to be taken into account when recording transmission holograms. If these reflections are not eliminated, unwanted secondary gratings are stored due to interference of the object and reference beams with the beams reflected at the interface. This not only gives rise to an anti-aesthetic effect, but also produces a reduction in diffraction efficiency and an increase in noise. We present the results obtained using a method which eliminates these unwanted reflections. This method, instead of using liquids, makes use of a black self-adhesive PVC masking tape stuck on the glass side of the holographic plate. We carried out a qualitative analysis of the different results obtained for plates with and without black PVC tape and also quantitatively analyzed the effect of the tape on the reflectivity of the plates as well as the density of holographic gratings. The results obtained confirm the applicability of the method described for antihalation reduction and elimination of unwanted reflections that cause interference affecting the quality of the holographic image.     

大景深多重全息术及其应用

提出并实现服用一般Ｈｅ－Ｎｅ激光器记录的大景攀重全息术，这种技术是根据光源时间相干性的特点，在参考光上作光路补偿来扩大景深，并用旋转光楔调制两平面参考波，记录大景深物场的多重全息图，这是一种重像数可以选择的大景深多重全息术，文中给出理论分析和实验结果，理论分析与实验结果是吻合的，文中还提出了用旋转光楔实现多路多参考光编码记录的多通道大景深全息干涉计量术，这种技术可用于研究大景深物场的时间序列动态过     

Modified phase contrast for recording of holographic optical elements

A modified phase contrast method is described for the fabrication of holographic optical elements with in-line diffraction patterns. In this method, a liquid crystal phase modulator is addressed by computer-generated holograms to achieve variable phase gratings. The phase gratings are imaged onto photosensitive material by a phase contrast method without a Fourier filter. We show the analytical treatment of the modified phase contrast method and demonstrate the application in holographic recording.     

Narrow-band holographic interference LiNbO3-based filters

New experimental data on antiparallel-beam holograms recorded in LiNbO₃, temperature fixation of the recorded holographic gratings, and the spectral characteristic of a narrow-band (0.01 nm) interference filter are reported. The effects of asymmetry in the diffraction efficiency and the emergence of satellites in the transmission spectrum of the filter are observed. These effects are explained using the birefringence properties of the crystal and the ability of holograms to transfer power between the beams in the course of recording.     

Control of the Rendition Wavelength Shifts of Color Lippmann Holograms Recorded in Single-layer panchromatic Silver-halide Emulsion

Russian PFG-03C panchromatic ultra-high resolution silver-halide emulsion is regarded as the most successful material for the fabrication of color reflection holograms. But the lack of established and reliable processing sequences prevents its practical applications in business and everyday life. Though much attention is drawn upon the processing of PFG-03C color reflection holograms, the color desaturation is still a problem. The article describes the new processing of color holograms recorded in PFG- 03C plates which is demonstrated experimentally to have the capacity of controlling the rendition wavelength shifts and improving the color desaturation effectively. The rendition spectra of Red-Green-Blue (R. G. B. ) single-line reflection holographic gratings, and the color reflection hologram as well, are given in this paper.     

Polarization reflection holographic gratings in azobenzene-containing gelatine films

We have written polarization reflection holograms in an azobenzene-containing material. Two waves with circular polarization were used to record the gratings; the light resulting from their overlap induces chirality in the samples. The holographic reflection of the polarization gratings has the properties of Bragg reflection in cholesteric liquid crystals.     

高质量全息光栅实验系统研究

基于全息光栅在信息光学及光谱仪中的重要地位,对全息光栅进行了理论分析,提出了一种新的制作高质量全息光栅的实验系统.该实验系统的优点在于:将激光器发出的高斯光束改造成为均匀平面光波,以此平面光波作为光源可以制作出高质量的全息光栅.     

Study of effective optical thickness in photopolymer for application

The impact of the effective optical thickness of a photopolymer on its holographic performance was studied. To overcome the attenuation of gratings for a better uniformity, a multilayer approach was introduced, by adjusting concentrations of dye along the depth of photopolymer to compensate the attenuation of recording light due to absorption. Multilayer photopolymers with thicknesses over 500 μm were designed, fabricated, and characterized experimentally, exhibiting better Bragg selectivity. More holograms were stored in multilayer material by angular multiplexing, and the cumulative grating strength was enhanced, leading towards larger holographic storage capacity.     

制造全息光栅的新装置

本文报道一种利用洛埃镜原理制造全息光栅的新装置及其调整方法.该装置具有光学系统简单,干涉条纹定位精度高和调整方便等优点,可制造性能良好的全息光栅.     

A simple two-ray interferometer based on a beamsplitter cube

Results of analysis of a very simple, compact interferometer for recording holographic diffraction gratings, which allows continuous tuning of the angle between the interfering beams from 0° to 80°, are presented. The device consists of a single optical element, a beamsplitter cube. The lengths of arms in such an interferometer are automatically equal, and tuning is accomplished by changing the angle of incidence of the beam on the input face. Formulas for calculating the principal characteristics of the device are derived. It is shown that using a cube material with a higher index of refraction allows increasing the beam diameter and broadening the tuning range. Recommendations on the device design are provided.     

Sorting and detecting orbital angular momentum states by using a Dove prism embedded Mach-Zehnder interferometer and amplitude gratings

An experimental system consisting of a Dove prism embedded Mach-Zehnder (M-Z) interferometer and two gratings was built to sort and detect orbital angular momentum (OAM) states of light beams. The helical beams with different OAM states were generated by propagating the fundamental-mode Gaussian beam through a spatial light modulator. The Dove prism embedded M-Z interferometer was used to sort helical beams with odd or even OAM number and two binary amplitude gratings were used to measure the OAM states. Sorting of coaxially-superposed coherent and incoherent helical beams with odd and even OAM states was realized in the experiment.     

Analysis of multiplexed holograms stored in a thick PVA/AA photopolymer

Multiplexing many holograms in photopolymers over 500 μm thick poses many problems associated with Beer’s law. In fact, the commercial holographic films (Aprilis and Inphase for example) are around 300 μm thick. For this range of thickness of absorbent photopolymeric materials, the gratings are recorded using all the thickness of the layer. Since the optical thicknesses of the multiplexed gratings are similar, it is easy to obtain an optimized time schedule to maximize the capacity of the material. For large thicknesses, the different effective optical thickness of each hologram requires an accurate prediction of each effective optical thickness in order to determine the minimum separation necessary between two consecutive multiplexed holograms. In this study, we have checked the experimental utility of the schedule model presented in a previous study to predict the multiplexing process of many gratings in a PVA/acrylamide photopolymer.     

Investigation of the spectral selectivity of volume holograms with femtosecond pulsed radiation

A method for studying the parameters of high-selectivity volume holograms and photonic crystal structures using ultrashort pulsed radiation in a wide spectral range is developed. The experimental system and measurement procedure are described. The results of determination of the diffraction efficiency and spectral selectivity of holographic gratings with spatial frequencies of 360 and 640 mm^?1 are presented. The parameters of the holograms determined by the method proposed and by the conventional techniques based on the use of continuous laser radiation are found to coincide.     

Spectral selectivity of holographic mirrors recorded in an attenuating medium

Numerical simulation of the optical properties of unslanted reflection holographic gratings (holographic mirrors) is made by the characteristic matrix method. The holograms are recorded in an attenuating medium but the reconstruction is that of pure phase structures in which the refractive index depends exponentially on the exposure. The dependence of the hologram spectral selectivity on medium absorption, amplitude ratio of the two interference waves and recording linearity is studied.     

利用傅里叶变换全息图实现彩色胶片存储

本文提出一种利用傅里叶变换全息图存储彩色胶片的方法.在参考光路和透明片后置入采栅,以红、绿、蓝三种波长记录+1级谱的点全息图.当三色光分别照明各自的全息图时,可再现两个真彩色图像.     

Demonstration of a spectrally scanned holographic Stokesmeter

A holographic Stokesmeter (HSM) utilizes the inherent polarization sensitivity of volume gratings to determine all the Stokes parameters of input beams. A unique feature of the HSM is that it can be designed for spectral multiplexing at a high speed. Here, we report the demonstration of such a spectrally scanning HSM for two different wavelengths. Integration of such an HSM with a polarimetric imaging system will produce a device of potentially significant practical usage: a multi-spectral Stokes parameter camera (MSPC).     

Holographic grating recorded by He–Ne laser operating at 632.8 nm in polymer film containing push–pull azo dye

Holographic gratings were optically recorded by two beams from a He–Ne laser operating at 632.8 nm in poly (methyl methacrylate) (PMMA) film containing push–pull azo dye. The holographic characteristics of the recorded gratings were dependent on the polarization direction of the recording beams and the relationship between the diffractive signals and the power density of recording beams was investigated. The formation of holographic gratings accompanied by 532 nm (double-frequency of Nd:YAG laser) irradiation was studied in detail. It was found that the effect of 532 nm laser to the holographic grating lay in two aspects. The acceleration effect of 532 nm laser to the formation of holographic grating is predominant when the power density of 532 nm laser is low. While at relatively high power density of 532 nm laser, the erasure is the main factor to the holographic grating. Moreover, the holographic grating was probed by 532 nm laser at low power density and the dependence of the first order diffractive signal on the recording beam power density was also presented.     

Shift multiplexing with a two-dimensional lens array

We propose a new shift multiplexing method to reduce the cross-talk noise and increase the holographic storage density. We use spherical waves emerging from a two-dimensional lens array as reference beams to multiple holograms. The theoretical results indicate that the sidelobes of the diffraction intensity can sharply be reduced to near-zero and the spatial separation of adjacent holograms can also be reduced, resulting in higher holographic storage density than conventional shift multiplexing methods.     

高质量全息光栅的制作

全息光栅由感光版记录高斯光束干涉条纹制得 ,干涉条纹的不等宽性降低了光栅品质。制取高质量全息光栅的关键是要用均匀平面波作光源。在分析干涉区内光强分布的基础上 ,给出了制作等周期正弦全息光栅的两种方法 :限制曝光区大小的方法和高斯光束强度均匀化的方法。