Special Issue "Advanced Materials for Modern Holographic Applications"

Guest Editor
Prof. Dr. Martin Fally
Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Wien, Austria
Website: http://fun.univie.ac.at
E-Mail:
Phone: +43 1 4277 511 10
Fax: +43 1 4277 511 81
Interests: neutron diffraction by light-induced gratings; neutron interferometry; photorefraction in centrosymmetric crystals; holographic scattering; anisotropic recording

Guest Editor
Prof. Dr. Mirco K. Imlau
Fachbereich Physik, Universität Osnabrück, Barbarastrasse 7, D-49069 Osnabrück, Germany
Website: http://www.imlau.physik.uni-osnabrueck.de
E-Mail:
Interests: light-matter-interactions; dynamical holography; (ultra-)fast spectroscopy; nonlinear optics & photonics

Dear Colleagues,

Driven by the impact of the holographic principle and the field of visionary holographic applications (real-time 3D-display devices, (ultra-) high density volume data storage, 3D-microscopy at the atomic scale), several research groups have focussed their work on the study and development of appropriate holographic materials in recent years. This trend has been fostered by the progress obtained in the fields of nanoscience and nanotechnology, because novel approaches for targeted material design on the sub-wavelength scale became possible (bottom-up approach, hybrid nano-materials, etc.).

As a result, we recognize a variety of advanced materials today that are applicable for modern holography. The latter includes recording and subsequent reconstruction using e.g., (ultra-)short laser pulses, electrons, X-rays or neutrons. Such advanced materials typically are far beyond the class of well-established materials, e.g., films whose function is based on chemical post-processing or crystals featuring the photorefractive effect.

It is the aim of this Special Issue to collect information on the most recent developments of advanced materials providing high potential for modern holography. These materials might be diverse and range from semiconductors with DX-centers to molecular crystals with photo-induced linkage isomerism to materials that can be explored using neutron holography with atomic resolution. Included are also functionalized materials with extended holographic properties such as e.g., holographic polymer dispersed liquid crystals, optically addressable liquid crystal elastomers or nanoparticle-polymer composites.

We further seek for contributions that address the field of visionary applications enabled by these materials.

This Special Issue is intended to represent the first step of establishing an international platform for researchers who are focusing on advanced materials for modern holographic applications.

Prof. Dr. Martin Fally
Prof. Dr. Mirco K. Imlau
Guest Editors

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• advanced holographic recording materials & optical storage media
• polymer dispersed liquid crystals
• nanoparticle polymer composites
• liquid crystals elastomers
• composite polymeric materials
• photosensitive glasses
• photoinduced metastable states
• photo-isomerization
• matter wave diffractive optics and holography (X-rays, neutrons, electrons)
• holographic optical elements

Type of Paper: Review
Title: Aspects of the Performance of Nematic LCOS Devices for Dynamic Holography
Authors: Neil Collings, Bill Crossland, Daping Chu, Tony Davey, John Moore, Mike Pivnenko and Ivonne Medina-Salazar
Affiliation: Department of Engineering, University of Cambridge, Cambridge, UK; E-Mail: nc229@cam.ac.uk (N.C.)
Abstract: Electroholography offers a flexible approach to the realization of programmable media of high space bandwidth product. Liquid crystals on silicon spatial light modulators provide more than a wavelength of phase modulation and greater than a million pixels of complexity. They have been used for both 2D and 3D holographic display and for precise beam steering in optical switches. This paper covers current research in improving device performance in view of the applications which will benefit from them. In particular, the resolution and speed limitations of current devices, and the noise issues related to spatially and multilevel quantized holograms will be summarised. In contrast to optically recorded holograms, there is a large flexibility in the programming of the kinoform which will be displayed. The algorithms which are used to calculate the kinofrom will be reviewed and the projected performance for future devices assessed.
Keywords: dynamic holography; liquid crystal on silicon; spatial light modulator

Title: Liquid Crystalline Cyanobiphenyl Homologues with Enhanced by Doped Gold Nanoparticles Display Parameters
Authors: K. K. Vardanyan et al.
Affiliation: Department of Physics, Rutgers University-Camden, Camden, NJ 08102, USA; E-Mail: kvardany@camden.rutgers.edu
Abstract: We study the dispersion of gold nanoparticles (GNP) in different homologues of cyanobiphenyl liquid crystals (nCB). We show that doped GNP dramatically affects the material and consequently display parameters, and mesophase stability of these mainly room temperature nematics. We report several homologes at certain GNP percentages with a few times lower (then their values for pure nematics), switching voltages and times, and with broader operational thermal range. These materials are good candidates for their applications in LC display devices. They could be also utilized in holographic polymer dispersed liquid crystals (H-PDLC) which demand fast switching and big optical birefringence. We show that the amount of carbon atoms n in alkyl “tail” of the homologues constituent molecules and the concentration of dispersed GNP critically affect the behaviour of material parameters in nanocomposites. We propose that the influence of GNP on material parameters and thermal stability of the nematics is caused by formation of different kind of aggregations between nanoparticles and LC molecules. These clusters affect the local ordering of LC molecules consequently changing the material parameters and mesophase stability. Performed computer simulations of intramolecular pair interaction energies and thermodynamic parameters using Monte Carlo method articulate our proposed model.
Keywords: liquid crystal nanocomposites; electro-optics of nematics; holography and liquid crystals; cluster formation in liquid crystals

Title: Interrogation of Composite Defects with Holography
Author: Rikard B. Heslehurst
Affiliation: School of Engineering and Information Technology, University College UNSW, Australian Defence Force Academy, Canberra, ACT, Australia; E-Mail: r.heslehurst@adfa.edu.au
Abstract: In any structural component where load path is diverted due to a change in local geometry or properties, i.e. a delaminated composite component, where out-of-plane stresses maybe induced, component surface displacements will occur. These out-of-plane surface displacements, although relatively small, are indicative of internal structural problems that can be associated with component strength capacity limitations. This discussion is of the application of a portable holographic interferometry testing system (PHITS) to study micro-deformations of a surface in a wide range of structural defects in composite materials. For composite materials the area of interest in the study are; inter-ply cracks (delaminations), intra-ply cracks (fibre/matrix interface separation), matrix degradation due to excessive heat, and fibre cuts and fracture. The results of this optical experimental investigation have extended structural behaviour and structural mechanics understanding of the defects in composite materials studied. In particular, the influence of the delaminated composite sub-laminate’s anisotropy on the buckled surface shape was clearly observed, and thus understood to a greater level. This investigation has extensively demonstrated the practical use of PHITS as an NDI technique for a better understanding of component structural mechanics. During the research several other areas of application and further understanding were founded and are currently being pursued.

Type of Paper: Review
Title: Semiconductor CdF₂:Ga and CdF₂:In Crystals as Media for Real-Time Holography
Authors: Alexander I.  Ryskin, Alexander S. Shcheulin and Alexander E. Angervaks
Affiliation: National Research University ITMO, St. Petersburg, Russia; E-Mail: angervax@mail.ru (A.E.A.)
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 the ground (“deep”) state by a barrier. Photo-induced 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 up to 10 MHz. 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.
Keywords: cadmium fluoride; bistable centers; photoinduced metastable state; holographic grating decay; real-time holography; dynamic correction of wavefronts and optical images; holographic correlator

Title: Advanced Materials for Modern Holographic Applications
Authors: Volker Dieckmann, Sebastian Eicke, Kristin Springfeld, and Mirco Imlau
Affiliation: Department of Physics, University of Osnabrück, Barbarastr. 7, 49069 Osnabrück, Germany; E-Mail: vdieckma@uos.de
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 sup-ps regime and lifetimes from microseconds up to hours at room temperature. This article reviews 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.

Title: Biophotopol: A Sustainable Photopolymer for Holographic Data Storage Applications
Authors: M. Ortuño ^1,2, S. Gallego ^1,2, A. Márquez ^1,2, C. Neipp ^1,2, I. Pascual ^2,3 and A. Beléndez ^1,2,*
Affiliations: ¹ Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante, Apartado 99, E03080 Alicante, Spain; E-Mail: a.belendez@ua.es
² Instituto Universitario de Física Aplicada a las Ciencias y las Tecnologías, Universidad de Alicante, Apartado 99, E03080 Alicante, Spain
³ Departamento de Óptica, Farmacología y Anatomía, Universidad de Alicante, Apartado 99, E03080 Alicante, Spain
Abstract: Photopolymers have proved to be useful for different holographic applications such as holographic data storage or holographic optical elements. However, most photopolymers have some undesirable features, such as the toxicity of some of their components or their low environmental compatibility. In this sense the Holography and Optical Processing Group from the University of Alicante has developed a new dry photopolymer with low toxicity and high thicknesses, known as biophotopol, which is very adequate for applications related to holographic data storage. In this paper we present the main characteristics of this material in a compilation of the last studies on biophotopol.
Keywords: holography; holographic recording materials; photopolymers; low toxicity

Title: Transition Metal Compounds Towards Holography
Authors: Volker Dieckmann, Sebastian Eicke, Kristin Springfeld, and Mirco Imlau
Affiliation: Department of Physics, University of Osnabrück, Barbarastr. 7, 49069 Osnabrück, Germany; E-Mail: vdieckma@uos.de
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 sup-ps regime and lifetimes from microseconds up to hours at room temperature. This article reviews 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.