Research

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1614 KiB

Open AccessArticle

Holographic Spectroscopy: Wavelength-Dependent Analysis of Photosensitive Materials by Means of Holographic Techniques

by Kay-Michael Voit and Mirco Imlau

Materials 2013, 6(1), 334-358; https://doi.org/10.3390/ma6010334 - 23 Jan 2013

Cited by 10 | Viewed by 8030

Holographic spectroscopy is highlighted as a powerful tool for the analysis of photosensitive materials with pronounced alterations of the complex permittivity over a broad range in the visible spectrum, due to the advances made both in the fields of advanced holographic media and [...] Read more.

Holographic spectroscopy is highlighted as a powerful tool for the analysis of photosensitive materials with pronounced alterations of the complex permittivity over a broad range in the visible spectrum, due to the advances made both in the fields of advanced holographic media and highly tunable lasers systems. To analytically discuss consequences for in- and off-Bragg reconstruction, we revised Kogelnik’s coupled wave theory strictly on the basis of complex permittivities. We extended it to comply with modern experimental parameters such as out-of-phase mixed holograms and highly modulated gratings. A spatially modulated, wavelength-dependent permittivity that superimposes a spatially homogeneous wavelength-dependent ground state spectrum is taken into account for signal wave reconstruction with bulky elementary mixed gratings as an example. The dispersion characteristics of the respective diffraction efficiency is modelled for color-center-absorption and absorption of strongly localized carriers. As an example for the theoretical possibilities of our newly derived set of equations, we present a quantitative analysis of the Borrmann effect connected to out-of-phase gratings, providing easier and more intuitive methods for the derivation of their grating parameters. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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583 KiB

Open AccessArticle

Quickly Updatable Hologram Images Using Poly(N-vinyl Carbazole) (PVCz) Photorefractive Polymer Composite

by Naoto Tsutsumi, Kenji Kinashi, Asato Nonomura and Wataru Sakai

Materials 2012, 5(8), 1477-1486; https://doi.org/10.3390/ma5081477 - 22 Aug 2012

Cited by 35 | Viewed by 7164

Abstract

Quickly updatable hologram images using photorefractive (PR) polymer composite based on poly(N-vinyl carbazole) (PVCz) is presented. PVCz is one of the pioneer materials of photoconductive polymers. PR polymer composite consists of 44 wt % of PVCz, 35 wt % of 4-azacycloheptylbenzylidene-malonitrile [...] Read more.

Quickly updatable hologram images using photorefractive (PR) polymer composite based on poly(N-vinyl carbazole) (PVCz) is presented. PVCz is one of the pioneer materials of photoconductive polymers. PR polymer composite consists of 44 wt % of PVCz, 35 wt % of 4-azacycloheptylbenzylidene-malonitrile (7-DCST) as a nonlinear optical dye, 20 wt % of carbazolylethylpropionate (CzEPA) as a photoconductive plasticizer and 1 wt % of 2,4,7-trinitro-9-fluorenone (TNF) as a sensitizer. PR composite gives high diffraction efficiency of 68% at E = 45 V μm⁻¹. Response speed of optical diffraction is the key parameter for real-time 3D holographic display. The key parameter for obtaining quickly updatable holographic images is to control the glass transition temperature lower enough to enhance chromophore orientation. Object image of the reflected coin surface recorded with reference beam at 532 nm (green beam) in the PR polymer composite is simultaneously reconstructed using a red probe beam at 642 nm. Instead of using a coin object, an object image produced by a computer was displayed on a spatial light modulator (SLM) and used for the hologram. The reflected object beam from an SLM was interfered with a reference beam on PR polymer composite to record a hologram and simultaneously reconstructed by a red probe beam. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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271 KiB

Open AccessArticle

Replication of Holograms with Corn Syrup by Rubbing

by Nildia Y. Mejias-Brizuela, Arturo Olivares-Pérez and Mauricio Ortiz-Gutiérrez

Materials 2012, 5(8), 1462-1476; https://doi.org/10.3390/ma5081462 - 21 Aug 2012

Cited by 4 | Viewed by 5812

Abstract

Corn syrup films are used to replicate holograms in order to fabricate micro-structural patterns without the toxins commonly found in photosensitive salts and dyes. We use amplitude and relief masks with lithographic techniques and rubbing techniques in order to transfer holographic information to [...] Read more.

Corn syrup films are used to replicate holograms in order to fabricate micro-structural patterns without the toxins commonly found in photosensitive salts and dyes. We use amplitude and relief masks with lithographic techniques and rubbing techniques in order to transfer holographic information to corn syrup material. Holographic diffraction patterns from holographic gratings and computer Fourier holograms fabricated with corn syrup are shown. We measured the diffraction efficiency parameter in order to characterize the film. The versatility of this material for storage information is promising. Holographic gratings achieved a diffraction efficiency of around 8.4% with an amplitude mask and 36% for a relief mask technique. Preliminary results using corn syrup as an emulsion for replicating holograms are also shown in this work. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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590 KiB

Open AccessArticle

Volume Holograms in Photopolymers: Comparison between Analytical and Rigorous Theories

by Sergi Gallego, Cristian Neipp, Luis A. Estepa, Manuel Ortuño, Andrés Márquez, Jorge Francés, Inmaculada Pascual and Augusto Beléndez

Materials 2012, 5(8), 1373-1388; https://doi.org/10.3390/ma5081373 - 15 Aug 2012

Cited by 16 | Viewed by 6223

Abstract

There is no doubt that the concept of volume holography has led to an incredibly great amount of scientific research and technological applications. One of these applications is the use of volume holograms as optical memories, and in particular, the use of a [...] Read more.

There is no doubt that the concept of volume holography has led to an incredibly great amount of scientific research and technological applications. One of these applications is the use of volume holograms as optical memories, and in particular, the use of a photosensitive medium like a photopolymeric material to record information in all its volume. In this work we analyze the applicability of Kogelnik’s Coupled Wave theory to the study of volume holograms recorded in photopolymers. Some of the theoretical models in the literature describing the mechanism of hologram formation in photopolymer materials use Kogelnik’s theory to analyze the gratings recorded in photopolymeric materials. If Kogelnik’s theory cannot be applied is necessary to use a more general Coupled Wave theory (CW) or the Rigorous Coupled Wave theory (RCW). The RCW does not incorporate any approximation and thus, since it is rigorous, permits judging the accurateness of the approximations included in Kogelnik’s and CW theories. In this article, a comparison between the predictions of the three theories for phase transmission diffraction gratings is carried out. We have demonstrated the agreement in the prediction of CW and RCW and the validity of Kogelnik’s theory only for gratings with spatial frequencies higher than 500 lines/mm for the usual values of the refractive index modulations obtained in photopolymers. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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379 KiB

Open AccessArticle

Biophotopol: A Sustainable Photopolymer for Holographic Data Storage Applications

by Manuel Ortuño, Sergi Gallego, Andrés Márquez, Cristian Neipp, Inmaculada Pascual and Augusto Beléndez

Materials 2012, 5(5), 772-783; https://doi.org/10.3390/ma5050772 - 02 May 2012

Cited by 30 | Viewed by 6645

Abstract

Photopolymers have proved to be useful for different holographic applications such as holographic data storage or holographic optical elements. However, most photopolymers have certain undesirable features, such as the toxicity of some of their components or their low environmental compatibility. For this reason, [...] Read more.

Photopolymers have proved to be useful for different holographic applications such as holographic data storage or holographic optical elements. However, most photopolymers have certain undesirable features, such as the toxicity of some of their components or their low environmental compatibility. For this reason, the Holography and Optical Processing Group at the University of Alicante developed a new dry photopolymer with low toxicity and high thickness called biophotopol, which is very adequate for holographic data storage applications. In this paper we describe our recent studies on biophotopol and the main characteristics of this material. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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650 KiB

Open AccessArticle

Kinetics of Holographic Recording and Spontaneous Erasure Processes in Light-Sensitive Liquid Crystal Elastomers

by Marko Gregorc, Hui Li, Valentina Domenici, Gabriela Ambrožič, Martin Čopič and Irena Drevenšek-Olenik

Materials 2012, 5(5), 741-753; https://doi.org/10.3390/ma5050741 - 25 Apr 2012

Cited by 10 | Viewed by 6594

Abstract

The optical mechanism for imprinting one-dimensional grating structures into thin films of a light-sensitive monodomain liquid crystal elastomer is investigated by analyzing the time dependence of optical diffraction properties. The recording kinetics shows an irregular oscillatory behavior, which is most expressed at small [...] Read more.

The optical mechanism for imprinting one-dimensional grating structures into thin films of a light-sensitive monodomain liquid crystal elastomer is investigated by analyzing the time dependence of optical diffraction properties. The recording kinetics shows an irregular oscillatory behavior, which is most expressed at small grating spacings and at temperatures close to the nematic-isotropic phase transition. The oscillations are attributed to the opto-mechanical response of the film, i.e., to contraction of the film during the recording process. At temperatures far below the nematic-isotropic phase transition, the spontaneous erasure kinetics exhibits exponential relaxation with relaxation time following the Arrhenius activation law. However, at temperatures close to the nematic-isotropic phase transition, the erasure process shows an interesting nonmonotonic behavior that we attribute to the non-linear relation between the concentration of the photo-transformed chemical groups and the nematic order parameter. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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2046 KiB

Open AccessArticle

Optical Properties of Mg, Fe, Co-Doped Near-Stoichiometric LiTaO₃ Single Crystals

by Wei Tse Hsu, Zhi Bin Chen, Chien Cheng Wu, Ravi Kant Choubey and Chung Wen Lan

Materials 2012, 5(2), 227-238; https://doi.org/10.3390/ma5020227 - 30 Jan 2012

Cited by 24 | Viewed by 7016

Abstract

Mg, Fe co-doped near-stoichiometric lithium tantalite (SLT) single crystals were grown by employing the zone-leveling Czochralski (ZLCz) technique. The optical properties, holographic parameters, as well as the composition of the grown crystals were measured. It was found that the Li/Ta ratio decreased with [...] Read more.

Mg, Fe co-doped near-stoichiometric lithium tantalite (SLT) single crystals were grown by employing the zone-leveling Czochralski (ZLCz) technique. The optical properties, holographic parameters, as well as the composition of the grown crystals were measured. It was found that the Li/Ta ratio decreased with the doping of Mg and Fe ions. A red shift was observed in absorption spectrum for the Mg, Fe co-doped crystals compared to the undoped and Mg-doped ones. The effect of the iron ions (Fe²⁺ and Fe³⁺) was further discussed based on the specified absorption bands. Moreover, the occupation mechanism for the defects was discussed by using the IR absorption spectrum, which was attributed to the Fe_Ta³⁻ defects in the highly Fe-doped crystal. In addition, the holographic parameters were also found to be improved with a higher Fe/Ta ratio in the crystals. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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Review

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3968 KiB

Open AccessReview

Holographic Gratings for Slow-Neutron Optics

by Juergen Klepp, Christian Pruner, Yasuo Tomita, Peter Geltenbort, Irena Drevenšek-Olenik, Saso Gyergyek, Joachim Kohlbrecher and Martin Fally

Materials 2012, 5(12), 2788-2815; https://doi.org/10.3390/ma5122788 - 12 Dec 2012

Cited by 25 | Viewed by 7091

Abstract

Recent progress in the development of holographic gratings for neutron-optics applications is reviewed. We summarize the properties of gratings recorded in deuterated (poly)methylmethacrylate, holographic polymer-dispersed liquid crystals and nanoparticle-polymer composites revealed by diffraction experiments with slow neutrons. Existing and anticipated neutron-optical instrumentations based [...] Read more.

Recent progress in the development of holographic gratings for neutron-optics applications is reviewed. We summarize the properties of gratings recorded in deuterated (poly)methylmethacrylate, holographic polymer-dispersed liquid crystals and nanoparticle-polymer composites revealed by diffraction experiments with slow neutrons. Existing and anticipated neutron-optical instrumentations based on holographic gratings are discussed. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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362 KiB

Open AccessReview

Recent Advances in the Photorefraction of Doped Lithium Niobate Crystals

by Yongfa Kong, Shiguo Liu and Jingjun Xu

Materials 2012, 5(10), 1954-1971; https://doi.org/10.3390/ma5101954 - 22 Oct 2012

Cited by 78 | Viewed by 7891

Abstract

The recent advances in the photorefraction of doped lithium niobate crystals are reviewed. Materials have always been the main obstacle for commercial applications of photorefractive holographic storage. Though iron-doped LiNbO₃ is the mainstay of holographic data storage efforts, several shortcomings, especially the [...] Read more.

The recent advances in the photorefraction of doped lithium niobate crystals are reviewed. Materials have always been the main obstacle for commercial applications of photorefractive holographic storage. Though iron-doped LiNbO₃ is the mainstay of holographic data storage efforts, several shortcomings, especially the low response speed, impede it from becoming a commercial recording medium. This paper reviews the photorefractive characteristics of different dopants, especially tetravalent ions, doped and co-doped LiNbO₃ crystals, including Hf, Zr and Sn monodoped LiNbO₃, Hf and Fe, Zr and Fe doubly doped LiNbO₃, Zr, Fe and Mn, Zr, Cu and Ce triply doped LiNbO₃, Ru doped LiNbO₃, and V and Mo monodoped LiNbO₃. Among them, Zr, Fe and Mn triply doped LiNbO₃ shows excellent nonvolatile holographic storage properties, and V and Mo monodoped LiNbO₃ has fast response and multi-wavelength storage characteristics. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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1296 KiB

Open AccessReview

Adaptive Holography in Liquid Crystal Light-Valves

by Umberto Bortolozzo, Stefania Residori and Jean-Pierre Huignard

Materials 2012, 5(9), 1546-1559; https://doi.org/10.3390/ma5091546 - 27 Aug 2012

Cited by 27 | Viewed by 6114

Abstract

By performing two-wave mixing experiments in a liquid crystal light-valve, optical beam amplification is obtained as a strongly resonant process to which a narrow frequency bandwidth is associated. This property is exploited to realize adaptive holographic interferometric systems able to efficiently detect displacements [...] Read more.

By performing two-wave mixing experiments in a liquid crystal light-valve, optical beam amplification is obtained as a strongly resonant process to which a narrow frequency bandwidth is associated. This property is exploited to realize adaptive holographic interferometric systems able to efficiently detect displacements as small as fraction of picometers. Pressure radiation induced deformations of a reflecting membrane are measured with the same type of system. Then, when used with complex wavefronts, like speckle fields, the LCLV-based interferometer allows to detect extremely small phase modulations. The examples shown demonstrate the potentialities of the light-valve for dynamic holography applications. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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5265 KiB

Open AccessReview

Transition Metal Compounds Towards Holography

by Volker Dieckmann, Sebastian Eicke, Kristin Springfeld and Mirco Imlau

Materials 2012, 5(6), 1155-1175; https://doi.org/10.3390/ma5061155 - 20 Jun 2012

Cited by 20 | Viewed by 7668

Abstract

We have successfully proposed the application of transition metal compounds in holographic recording media. Such compounds feature an ultra-fast light-induced linkage isomerization of the transition-metal–ligand bond with switching times in the sub-picosecond regime and lifetimes from microseconds up to hours at room temperature. [...] Read more.

We have successfully proposed the application of transition metal compounds in holographic recording media. Such compounds feature an ultra-fast light-induced linkage isomerization of the transition-metal–ligand bond with switching times in the sub-picosecond regime and lifetimes from microseconds up to hours at room temperature. This article highlights the photofunctionality of two of the most promising transition metal compounds and the photophysical mechanisms that are underlying the hologram recording. We present the latest progress with respect to the key measures of holographic media assembled from transition metal compounds, the molecular embedding in a dielectric matrix and their impressive potential for modern holographic applications. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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987 KiB

Open AccessReview

Semiconductor CdF₂:Ga and CdF₂:In Crystals as Media for Real-Time Holography

by Alexander I. Ryskin, Alexander S. Shcheulin and Alexander E. Angervaks

Materials 2012, 5(5), 784-817; https://doi.org/10.3390/ma5050784 - 07 May 2012

Cited by 2 | Viewed by 5949

Abstract

Monocrystalline cadmium fluoride is a dielectric solid that can be converted into a semiconductor by doping with donor impurities and subsequent heating in the reduction atmosphere. For two donor elements, Ga and In, the donor (“shallow”) state is a metastable one separated from [...] Read more.

Monocrystalline cadmium fluoride is a dielectric solid that can be converted into a semiconductor by doping with donor impurities and subsequent heating in the reduction atmosphere. For two donor elements, Ga and In, the donor (“shallow”) state is a metastable one separated from the ground (“deep”) state by a barrier. Photoinduced deep-to-shallow state transition underlies the photochromism of CdF₂:Ga and CdF₂:In. Real-time phase holograms are recorded in these crystals capable of following up optical processes in a wide frequency range. The features of photochromic transformations in CdF₂:Ga and CdF₂:In crystals as well as holographic characteristics of these media are discussed. Exemplary applications of CdF₂-based holographic elements are given. Full article

(This article belongs to the Special Issue Advanced Materials for Modern Holographic Applications)

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