Holographic Methods for the Investigation of Photochemical and Photophysical Properties of Molecules

Holography is most frequently thought of as a method of photography that results in three-dimensional images of the object being photographed. It is certainly true that this is the most visually spectacular aspect. But holography can also be used as a powerful tool for the investigation of a variety of photochemical and photophysical processes. These experimental techniques rely on the fact that small spatial modulations of a material's optical properties (index of refraction and absorption coefficient) can deflect an incident light beam into another direction. By following the growth or decay in intensity of this deflected beam, one can follow the underlying photochemical and photophysical processes producing the changes in optical properties. If a CW laser is used to produce the hologram one can use the technique to investigate solid state photochemistry. If a pulsed laser is used one can investigate a broad range of time dependent processes; energy transfer, diffusion, rotational relaxation, charge transport etc. Compared to conventional spectroscopic techniques the holographic method shows various advantages. So for example it is a highly sensitive zero-background technique and permits free choice of detection wavelength and detection beam intensity. As a result of information obtained using the holographic technique as a scientific tool, one can also find new classes of materials for the recording of holograms. This is the way in which two-photon four-level systems for hologram recording process gated on and off with an auxiliary source, and can be read with the infrared recording laser with no erasing of the hologram.     

Methods for investigation of holographic photopolymer materials

Results obtained by the authors on the development of holographic methods for investigation of photopolymer materials are presented. The work considers the methods for pulse recording of dynamic transmission gratings and characterization of hologram angular selectivity, the double-beam method of twophoton holographic recording, and heterodyne detection of inhomogeneities in volume holograms.     

KINETICS OF DYNAMIC HOLOGRAM RECORDING IN POLYMER FILMS WITH IMMOBILIZED BACTERIORHODOPSIN

Abstract— Polymer films with immobilized photosensitive membrane protein, bacteriorhodopsin (BR), were prepared and investigated. A sensitive holographic interferometer with phase modulated optical beams was used for investigation of kinetics of dynamic hologram recording in BR polymer films. It was found that phase hologram formation consisted of two quasi-exponential stages demonstrating existence of a diffusive process in obtained films. It was shown that the kinetics of a phase hologram recording by high intensity beams do not correlate with the exponential law. The applicability of BR polymer films as reversible photorefractive materials for dynamic holography and real-time interferometry was discussed.     

Metal ion doped polymers as media for optical memories

Polymer materials are making an impact on optical storage technology to develop high information density and fast access type memories with a high read-out efficiency. The principle and advantages of three-dimensional (3-D) data storage in the form of interference patterns (holograms) have been outlined. Three different information storage materials have been developed by doping metal ions such as Cr(VI) and Fe(III) in water-soluble polymers, namely poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA), which need no further thermal or chemical treatment. Volume transmission holograms have been recorded in dichromated poly(vinyl alcohol) (DCPVA), ferric chloride doped poly(vinyl alcohol) (FePVA) and dichromated poly(acrylic acid) (DCPAA), with and without an electron donor (dimethyl formamide), and xanthene dyes (fluorescein, eosin Y and Rose Bengal). Different parameters influencing the holographic performance have been optimized to achieve a high real-time diffraction efficiency (～70%). An electron transfer process from the polymer matrix to Cr(VI)/Fe(III), leading to the photocrosslinking of the polymer in the form of an interference pattern, has been suggested as the mechanism of information storage (hologram recording) in these materials.     

数字全息重构图像边缘误差抑制方法研究

数字全息技术由于其高灵敏度、高准确度、分辨能力强,且再现、存储及传输方便灵活等特点,在微纳结构与生物细胞的测量领域中得到越来越广泛的应用。然而,记录数字全息图受孔径有限等因素的影响,其重构图像会产生一些类似于波纹的边缘误差,导致成像质量降低和CCD视场不能充分利用。本文首先基于数字全息理论对误差产生原因进行了理论分析,并对边缘误差产生影响的数值参数进行了详细讨论,在此基础上,提出了一种周期延拓迭代方法对全息图进行预处理,并使用图像均方差值对迭代结果进行评价。通过计算机仿真与实验,结果表明,该方法能够显著降低边缘误差,提高再现图像质量。     

Direct Visualization of Electromagnetic Microfields by Superposition of Two Kinds of Electron Holograms

A new electron holographic method is presented to directly visualize pure phase objects such as electromagnetic microfields, which is achieved by superposition of two kinds of electron holograms. The method is very simple and is twice as sensitive as the conventional double-exposure electron holography and the four-electron-wave interference. Using this technique, an electric field around a charged latex sphere and a magnetic field around a barium ferrite particle have been directly observed.     

KINETICS OF DYNAMIC HOLOGRAM RECORDING IN POLYMER FILMS WITH IMMOBILIZED BACTERIORHODOPSIN

Abstract
Polymer films with immobilized photosensitive membrane protein, bacteriorhodopsin (BR), were prepared and investigated. A sensitive holographic interferometer with phase modulated optical beams was used for investigation of kinetics of dynamic hologram recording in BR polymer films. It was found that phase hologram formation consisted of two quasi-exponential stages demonstrating existence of a diffusive process in obtained films. It was shown that the kinetics of a phase hologram recording by high intensity beams do not correlate with the exponential law. The applicability of BR polymer films as reversible photorefractive materials for dynamic holography and real-time interferometry was discussed.     

Application of a novel photopolymer to a holographic head‐up display

A novel photopolymer for fabrication of high‐resolution volume holograms, which primarily are used on holographic optical elements such as head‐up display (HUD), is reported. This photopolymer consists of bisphenol‐type epoxy resin and radically polymerizable aliphatic monomer with diaryliodonium salt and 3‐ketocoumarin (KCD) as a complex initiator. The chemistry of imaging formation is based on the radical polymerization of the monomer initiated by a holographic exposure, following by the cationic polymerization of epoxy resin by UV‐exposure after post‐exposure baking. The yellowish color of hologram derived from KCD, the shape of peak of reconstructed light and the blue shift of wavelength of reconstructed light, were improved in order to satisfy the specifications for the combiner of HUD. A stand type holographic HUD system as an example of automotive display attached on the dashboard of an automobile is demonstrated. The display gives a high contrast image, and the combiner has good durability. Copyright © 1999 John Wiley & Sons, Ltd.     

Holographic Recording Media Based on Systems with Intramolecular and Intermolecular Charge Transfer

Information characteristics of holographic recording media based on poly(N-epoxypropylcarbazole) films containing charge-transfer systems as photogeneration sites were studied, in which donor and acceptor molecules (or their fragments) either formed adducts between one another or were covalently bound by polymethylene spacer groups or by a system of conjugated π bonds. The recording media based on compounds with intramolecular charge transfer over a system of conjugated bonds for recording holograms using the photothermoplastic method exhibit an narrower intense spectral sensitivity band and a high holographic sensitivity. In these media, the effect of prolonged storage of latent image before the development of a hologram was revealed and explained.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 4, 2005, pp. 297–306.Original Russian Text Copyright © 2005 by Davidenko, Ishchenko, Kostenko, Kuvshinskii, Kulinich, Melenevskii, D. Mysyk, R. Mysyk, Pavlov, Chuprina.     

Design concepts for diffusive holographic photopolymers

Diffusive photopolymers are an area of intense recent materials development, spurred by interest in holographic data storage, display holography, and custom diffractive optical elements, among other applications. This review examines a range of photopolymer formulations of academic and commercial interest, and places their design strategies in context via quantitative analysis of the recording fidelity, maximum refractive index change and the degree to which they achieve this limit. Finally, this analysis is extended to estimate the scope of achievable future performance improvements. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1021–1035.     

大数值孔径光学镜约束多级衍射机理

针对基于激光照明的离轴全息显微成像系统存在散斑和寄生条纹噪声,以及基于部分相干光照明的离轴数字全息显微技术存在相干条纹对比度差的问题,本文提出了一种基于单色LED照明的衍射相位显微成像系统。该系统利用大数值孔径物镜及光栅对物光进行多级衍射,并采用4f系统和空间滤波器分离出0级和+1级信息,分别作为参考光和物光,最终两束光在CCD阵面上干涉产生离轴全息图,从而形成共光路全息成像结构。通过理论分析和计算,对实验用到的光学元器件进行选型,确保衍射光频谱信息能够分开且满足抽样条件。最后与传统激光离轴数字全息显微成像检测结果进行对比,实验结果表明,本文提出的系统能够获得较高的成像准确度和信噪比。     

全色光致聚合物的全息记录 特性及应用研究

优选亚甲基蓝、曙红Y、吖啶橙分别作为红敏、绿敏、蓝敏光敏剂,制作出全色光致聚合物全息记录材料.全息记录特性测量表明,该材料在红、绿、蓝三基色激光记录下均具有大于90%的衍射效率和较高的感光灵敏度(70 mJ/cm²).开展了该材料的角度复用、波长复用全息存储实验,在材料的同一位置处分别以不同参物光夹角及不同记录波长成功存储了多幅全息图,且再现图像清晰明亮,相互之间无明显串扰,表明该材料具有良好的全息记录性能及应用价值.     

Polarization holographic optical recording based on a new photochromic diarylethene compound

A new unsymmetrical photochromic diarylethene, namely1-[2-methyl-5-(p-N,N-dimethylaminophenyl)-3-thienyl]-2-[2-methyl-5-(3-methoxylphenyl)-3-thienyl] perfluorocyclopentene (1a), was synthesized. The compound showed good photochromism, high sensitivity and remarkable fatigue-resistance both in solution and in poly(methyl methacrylate) (PMMA) matrix with UV/Vis light irradiation. The absorption maximum of its closed-ring isomer was observed at 624 nm in PMMA amorphous film. It is a nice match for the wavelength of the recording laser (633 nm). Using this target compound as recording medium, four types of polarization holographic optical recordings were performed successfully using a He-Ne laser. The results showed that only the orthogonal circular polarization recording could obtain a hologram with high diffraction efficiency and high signal-to noise-ratio. With multiplexing recording technology, three types of polarization multiplexing holographic optical recordings, including angular multiplexing, polarization multiplexing, and angular plus polarization multiplexing holographic recording, were also carried out perfectly based on its photoinduced anisotropic phenomenon accompanying the photochromic reaction by photoirradiation. The results demonstrate that the multiplexing recording technology is an effective method to improve recording capacity when using diarylethene 1 as recording medium.     

Cyclic allylic sulfide based photopolymer for holographic recording showing high refractive index modulation

The development and characterization of a new holographic photopolymer system showing high refractive index modulation (∆n) is presented. It exploits the ring-opening polymerization reaction of a cyclic allylic sulfide (CAS) monomer, which is dispersed in a cellulose acetate butyrate (CAB) polymer matrix together with a blue sensitive radical photoinitiator. Volume Phase Holographic Gratings (VPHGs) obtained using these films show a very good fidelity of the transferred pattern, without deviations from the theoretical curves. A high ∆n is obtained due to the addition to this system of a tetrafunctional thiol crosslinker, which maximizes the material potential (formula limit) of the formulation. It also allows for a thermal post process of the gratings, further enhancing the ∆n. The photopolymer properties are evaluated as function of the monomer and thiol concentration to determine the optimal composition, at which a ∆n greater than 0.03 is obtained. This is a considerably high value in the field of photopolymers for holography and it enables the manufacturing of efficient holograms.     

菲涅耳非相干相关数字全息研究进展

非相干数字全息术是当前国际前沿重要研究领域之一。传统全息术由于采用相干光源照明会在全息图记录过程中引入大量散斑噪声和寄生干涉,且对设备和记录条件要求很高,极大地限制了其应用范围。采用非相干光源照明的非相干全息术则可完全避免这些问题。菲涅耳非相干相关全息术是非相干全息术中最重要的类型之一。本文简要说明了菲涅耳非相干全息术的原理与特点,重点分析了该技术在抑制直流项和共轭像干扰、提高成像分辨率、改善再现像质量及相关应用等方面的研究进展。     

一种高质量的红敏光致全息记录材料的优化

应用全息技术的快速发展被有限的材料所限制,理想的全息记录材料应表现出理想的材料性能,如：高的灵敏度,高的分辨率,宽的广谱响应,高的相调制能力,好的环境稳定性,工艺过程和后处理方法容易又节约时间,但现在很少材料能够同时具有这些性能。重铬酸钾明胶有好的全息图     

The Experimental Study of Acrylamide Based Photopolymer Recording Materials for Applications in Optical Holography

Summary: The photopolymer recording material based on acrylamide monomer has been experimentally studied. After illumination with an interference field, the photopolymerization process is initiated and a diffraction grating is formed in real-time. The performance of the material depends on its chemical composition and recording parameters. Due to its self-developing characteristics, the real-time measurement of hologram formation is used for detection of the recording process. From the measurement, properties of the material can be determined and optimized for different holographic applications.     

Polymer network liquid crystal grating/Fresnel lens fabricated by holography

In this article, polymer network liquid crystal (PNLC) grating/Fresnel lens is fabricated by holography. The exposure light pattern for the grating is obtained by interfering two planar wave fronts, while the Fresnel pattern is achieved by interfering a planar wave front and a spherical wave front. Owing to the alignment effect and anchoring power of polymer network, the holographic PNLC grating achieves improved diffraction efficiency, and remarkably reduced operation voltage (reduced by 80%) compared with holographic polymer-dispersed-liquid-crystal and holographic polymer-stabilised blue-phase liquid-crystal gratings, while maintaining submillisecond response. Moreover, it achieves high spatial frequency with a 2-μm grating period, thanks to the holographic fabrication. The holographic PNLC Fresnel lens also exhibits attractive electro-optical properties.     

Holographic recording using visible-light sensitive polymers based on cationic polycondensation

Negative-working photopolymers based on a cationic polycondensation mechanism were developed. The photopolymers are highly sensitive to 488 nm argon ion laser light, because they use a chemically amplified reaction and are not sensitive to ambient oxygen. These photopolymers are composed of a poly(p-hydroxystyrene) matrix, a hexamethoxy methylmelamine crosslinker and a 2,4,6-tris(trichloromethyl)-1,3,5-triazine–coumarin dye combination as a photo-initiator. They exhibit 0.6 mJ/cm² (D^0.7_g) sensitivity to 488 nm light, as well as a high resolution of 0.5 μm. Due to their high sensitivity and high resolution, a relief-type hologram, larger than 50 × 50 cm, can be recorded in a short exposure time using them.     

Off-axis STEM or TEM holography combined with four-dimensional diffraction imaging.

Ultrahigh-resolution imaging may be achieved using modifications of the off-axis holography scheme in a scanning transmission electron microscopy (STEM) instrument equipped with one or more electrostatic biprisms in the illuminating system. The resolution is governed by the diameter of a reference beam, reduced by channeling through a line of atoms in an atomic-focuser crystal. Alternatively, the off-axis holography may be combined with the Rodenburg method in which a four-dimensional data set is obtained by recording a nanodiffraction pattern from each point of the specimen as the incident beams are scanned. An ultrahigh-resolution image is derived by computer processing to give a particular two-dimensional section of this data set. The large amount of data recording and data processing involved with this method may be avoided if the two-dimensional section is derived by recording the hologram while the four beams produced by two perpendicular biprisms are scanned in opposing directions across the specimen by varying the voltages on the biprisms. An equivalent scheme for conventional TEM is also possible. In each case, the complex transmission function of the specimen may be derived and resolutions of about 0.05 nm may be expected.