This PDF file contains the front matter associated with SPIE Proceedings Volume 7358, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Present and future of holography depends on the development of high quality holographic recording media. In this sense, the improvement of most of the applications associated with holography can be attributed to the optimization of the recording step in material. In this work we review holographic recording media as silver halide, photopolymers and sol-gel in which it has been demonstrated the possibility for achieving holographic storage and holographic optical elements. Photographic emulsions have high popularity in holographic recording, due to the high exposure sensitivity, the high resolving power and wide range of spectral sensitivity. In this work, recent advances in BB-640 Colorholographic photographic emulsion will be presented in transmission and reflection holographic gratings. Moreover photopolymers have been demonstrated as a high potential material in holographic optical storage. These materials do not need postprocessing, therefore they can be analyzed in real time. Furthermore, photopolymers have advantage such as the possibilities to be fabricated with high high thicknesses and with a wide spectral sensitivity range from the red to the blue region. As a result, high diffraction efficiency with excellent sensitivity can be obtained with the right choice of the monomers. Here we will present recent results with PVA-acrylamide composition. One of the drawbacks of the photopolymers is its thermomechanical stability, for this reason, sol-gel materials, a mixture of organic-inorganic material, have been recently developed. In this review we will present the experimental results in transmission and reflection holograms.

This paper reports on a new series of photochromic azobenzene-containing molecular glasses which are investigated as blending materials to improve the photochromic response of photoaddressable polymers. In order to identify potential candidates for blending, a variety of molecular glasses are synthesized and screened with respect to their photochromic response. Various end groups at the azobenzene chromophore and different core compounds are employed to obtain high thermal stability and good glass-forming properties as well as high sensitivity and refractive-index modulation. The best combination of structural variations is chosen to tailor a photoaddressable material with optimized physical and photophysical properties. By doping this photochromic molecular glass former into a photoaddressable polymer we are able to combine the high stability of polymer systems with the faster response of molecular glasses, thus creating a system which has the advantages of both material classes. With this approach we achieve an increase of the low photochromic sensitivity of the polymer, which is the biggest problem of these materials. In order to obtain a better understanding of the influence of the photochromic molecular glass former on the photochromic response in a polymer system we conduct holographic experiments on a concentration series of the glass former in an inert polymer matrix. By inscribing the holographic gratings at elevated temperatures we are able to increase the sensitivity of our molecular glass further.

Photopolymers are promising as holographic recording media as they are inexpensive, versatile materials, which can be made sensitive to a broad range of wavelengths. A deeper understanding of the processes, which occur during holographic grating formation in photopolymers, is necessary in order to develop a fully comprehensive model, which represents their behaviour. One of these processes is photo-initiation, whereby a photon is absorbed by a photosensitiser producing free radicals, which can initiate free radical polymerisation. These free radicals can also participate in polymer chain termination (primary termination) and it is therefore necessary to understand their generation in order to predict the temporally varying kinetic effects present during holographic grating formation. In this paper, a study of the photoinitiation mechanisms of Irgacure 784 dye, in an epoxy resin matrix, is carried out. This is achieved by analysing the temporal evolution of a series of simultaneously captured experimental transmittance curves, captured at different wavelengths, but at the same location, to enable the change in photon absorption during exposure to be estimated. We report on the experimental results and present a theoretical model to predict the physically observed behaviour.

Imaging tools for nanoscicence involving sub-100-nm scale objects have been dominated by atomic force microscopy (AFM), scanning tunneling microscopy (STM), and electron microscopy (SEM, TEM). These imaging techniques have contributed substantially to the development of nanoscience, providing a very powerful diagnostic tool capable of obtaining images with atomic resolution or as a subsidiary mechanism to arrange or modify surfaces also at the atomic scale [1,2]. However, some important problems have persisted traditional nanoscale imaging techniques. For example when scanning a nanometer size object that is not attached rigidly to a surface the interaction with the tip significantly perturbs the specimen degrading or eventually precluding the image acquisition. Electron microscopy often requires surface preparation, consisting of metallization of the sample to avoid surface charging. Additionally the metallization of the sample may alter its characteristics and also limits the resolution. In both cases, if the sample is large (millimeters in size) due to the limited field of view, the image obtained with these conventional methods is only representative of a very small portion of the object. Wavelength-limited holographic imaging using carbon nanotubes as the test object with a table-top extreme ultraviolet (EUV) laser operating at 46.9 nm will be discussed. The resolution achieved in this imaging is evaluated with a rigorous correlation image analysis and confirmed with the conventional knife-edge test. The nano-holography presented requires no optics or critical beam alignment; thus the hologram recording scheme is very simple and does not need special sample preparation. In holography, image contrast requires absorption to provide scattering by the illuminating beam. The EUV laser wavelength employed in this experiment (46.9nm) is advantageous because carbon based materials typically exhibit very small attenuation lengths, around 25 nm. The high absorption of even small object volumes produces high optical contrasts. The short attenuation length thus enables nearly full contrast for most objects without applying forces to the imaged objects, no charge buildup, and without the need for complicated sample preparation. Additionally this simple technique allows to image macroscopic size objects, several millimeters square with arbitrary shape while simultaneously sustaining across the image sub-50 nm spatial resolution. This characteristic is equivalent to storing data at a density rate of ~0.3 Tbit per square inch over large areas, and represents a simple demonstration of a method that allows permanently dense storage of a large amount of data.

A new image reconstruction scheme for coherence holography using a modified Sagnac-type radial shearing interferometer with geometric phase shift is proposed and experimentally demonstrated. The reconstruction of off-axis objects placed at different depths makes this proposed technique the most generic one. A reconstructed image, represented by a coherence function, can be visualized with a controllable magnification, which opens up a new possibility for a coherence imaging microscope.

We present a synthesized sub-ps dual-wavelength laser source for digital holographic interferometry with a wide reconstruction range. The developed laser source generates two spectrally separated parts within one pulse. The sub-ps pulse duration desensitizes the holographic setup to environmental impacts. A center wavelength distance of only 12 nm with a high contrast was demonstrated by spectral shaping of the 50 nm broad seed spectrum of a CPA Ti:sapphire laser system centered at 800 nm. Time-resolved two-wavelength contouring requires the simultaneous and separable recording of two holograms. In general, a single CCD-camera is applied, and the spectral separation is realized by different reference wave tilts, which requires ambitious interferometric setups. Contrary to this, we introduce two CCD-cameras for digital holographic recording, thus essentially simplifying the interferometric setup by the need of only one propagation direction of the reference wave. To separate the holograms for the simultaneous recording process, a Mach-Zehnder interferometer was extended by a polarization encoding sequence. To study our approach of time-resolved digital holographic two-wavelength contouring, an adaptive fluidic PDMS-lens with integrated piezoelectric actuator served as test object. The PDMS-lens consists of an oil-filled lens chamber and a pump actuator. If a voltage is applied to the piezoelectric bending actuator the fluid is pumped into the lens chamber which causes a curvature change of the 60-μm thick lens membrane and thus a shift of the focal length. The dynamic behavior of the PDMS-lens, driven at a frequency of 1 Hz, was investigated at a frame rate of 410 frames per second. The measured temporal change of the lens focal length between 98 and 44 mm followed the modulation of the piezoelectric voltage with a 30 V peak-to-peak amplitude. Due to the performed time-resolved two wavelength contouring, we are able to extract the optical path length differences between center and perimeter of the lens. From the calculated phase difference maps we estimated large optical path differences of larger than 10 μm, corresponding to more than 15 times of the source wavelength.

Polarization-holographic element on the basis of diffraction gratings with different profile of anisotropy for complete analysis of light, namely definition of all Stokes parameters of polarization ellipse is described. The polarizationholographic elements have many advantages compared to conventional devices of polarization optics: they make it possible to carry out the polarization analysis and transformation of light in real time; they operate in a wide spectral range without any need of modulation. A single element of the kind is as effective as the whole set of conventional analogues in polarization optics. We investigated the polarization-holographic gratings recorded by linearly polarized beams, and analyzed polarization of diffracted beams. For the recording, we used polarization-sensitive materials based on azodyes introduced in polymer matrices, developed by us. A complete analysis of the light, including the degree of polarization became also feasible with the help of polarization-holographic element based on the different type of polarization-holographic gratings.

In this paper, we review the optimization and characterization of a high-order harmonic generation (HHG) source for application in coherence imaging, and the use of this light source in a digital in-line holography setup. The high-order harmonic beam is generated by focusing a powerful infrared beam into an Ar gas cell. The length of the cell and the focusing parameters are optimized to maximize the HHG output. By spectrally filtering and focusing the generated harmonic beam and positioning a 2D detector, we obtain a table-top light source suitable for in-line holography, capable of recording a hologram with a single 40 fs XUV pulse. The reconstructed images have a spatial resolution in the micrometer range.

Our paper deals with the recent advances in synthetically written optical security devices (DOVIDs) and holograms. The synthesized holographic security elements are recorded with a resolution reaching 500.000 dpi and are specially developed for the "layman-level" security of the most important state valuables and documents, like banknotes and identity cards. We especially pay an attention to such holographic features being impossible to originate through conventional optical holography of matrix based devices.

Multi-layer diffraction structures with characteristic behavior in monochromatic and white light for the TM polarization that does not occur for the TE polarization are under study. They are composed of a thin film of silver, or the one with thin-film dielectric coatings over and/or under the film, and a pair of enclosing dielectric sheets. A periodic surface relief corrugates boundaries between neighboring layers. The structures are investigated in the transmission mode under various conditions of illumination by measuring the zero-order diffraction efficiency. Refractive indices of the enclosing sheets, of the dielectric coatings, and values of thickness of the latter are critical for high sensitivity to polarization. If such a structure is realized as a foil made of several layers, taking into account also a transparent adhesive fixing the foil to a substrate, the structure may become a promising device for protection of documents against counterfeiting. Theoretical analyses and experimental investigations of laboratory models and realized foil devices are presented.

In accordance with the development of various optical devices, an urgent need for innovative 3D microfabrication method arises. It requires not only rapid processing time or high energy efficiency but also high flexibility in designing 3D structure. Hence we established new 3D microfabrication method to satisfy all of these seemingly-contradictory factors. This method uses only single femtosecond laser pulse and phase CGH (computer generated hologram); the phase distribution of the pulse is controlled by the CGH and an arbitrary 3D microstructure is fabricated inside transparent material by multi photon absorption. It means that this method costs extremely short time and low power for the fabrication of an arbitrary complex 3D microstructure. In this report, the microfabrication of 3D spiral array which consists of 24 dot elements is demonstrated. It is very difficult to process multiple elements at different depths simultaneously, because the light intensity depends on the numerical aperture number of the objective lens and the distance from the CGH. Hence we improved the CGH calculation by considering these dependencies so that the light intensity of each element could be controlled separately. By this intensity adjustment, the shape of all elements becomes homogeneous. The other side of this intensity control is that it is able to process different shape elements intentionally by varying the intensity of each element. This intensity control is confirmed by the microfabrication with another CGH which forms 7 dot elements of different shapes. This result proves the high flexibility in designing 3D structure of this method.

According to the needs of creating holograms of 3D computer models, an original device for synthetizing non focused holograms has been designed and manufactured. The device composes holographic masters by projecting series of 2D views of a subject. These views are displayed by a SLM and projected through a special designed objective. The hologram is then subsequently recorded near the plane of the output pupil of the writing objective. The 3D holographic stereogram is then made by the H1-H2 copying. The main goal of the device is to create rainbow single parallax hologram masters. However, the device is able to write the holo-pixels in x-y directions, which allows us to use both parallaxes. This is used for the research in the field of RGB rainbow masters, reflection hologram masters and implementation of kinetics to the final stereogram. In this paper, the method and the design of the recording device is presented.

A method of optical design of hybrid optical systems by utilization the aplanatic condition is introduced here. The aplanatic condition was taken as a main optimizing criterion for the design of phase functions of diffractive optical elements during the optimization procedure. The phase function of the diffractive element can be arbitrary. We don't restrict ourselves to diffractive optical elements with a spherical phase function. Several hybrid optical systems, in particular hybrid doublets and hybrid triplets, consisting of one diffractive element and one or two refractive lenses, were designed and analyzed by this method.

Holography offer new nondestructive possibilities for bridging the gap between in vitro and in vivo measurements in dentistry, and thus increase the possibility of achieving more accurate and sometimes more objective diagnosis and therapy. The use of stone and plaster study models is an integral part of any dental practice and is required for research. Storage of study models is problematic in terms of space and cost. Various methods have been employed in the threedimensional (3D) assessment and recording of dental study models. These include Holography and Moire Topography. Holography was introduced in 1948. However, it was the work of Leith & Upatnieks that revolutionized holography with the application of the laser beam. Holography allows direct measurement of 3D displacements of a few micrometres. The major problem with this technique is the poor quality of recording the details of the study models, particularly in the incisor region. An advantage of holography is that films may be stored with medical records and it is a further step towards archiving dental study models. However, it cannot totally replace the original models. The aim of this study is to present the possibility to record dental models in holograms and to develop direct measurement on these. Key words: dentistry, dental model, holograms, fixed partial dentures, optical coherence tomography.

Different technologies can be used for fabrication of photonic crystals such as: self-assembly of colloidal particles, ebeam lithography (EB), interference lithography (IL) and focused ion beam (FIB). Among them, the holographic lithography (HL) is the only technique that is able to fabricate both two-dimensional and three-dimensional photonic crystals, as well as plasmonic structures, in large areas. In this paper we demonstrate the use of the multi-exposure of two-beam interference patterns, with rotation of the sample around different axis, for fabrication of large areas 2D and 3 D photonic crystals and plasmonic structures. Using this technique, we achieved aspect ratios of about 4 in 2D photoresist templates recorded in 1 cm² glass substrates. In order to generate the 2D photonic band gap layers and plasmonic structures, we combine the use the high aspect ratio photoresist templates with shadow evaporation of appropriated materials, with a further lift-off of the photoresist. The optical properties of the recorded structures, both photonic and plasmonic, were measured to demonstrate the applicability of the technique.

2-channel multiplexer/demultiplexer (Muxer/Demuxer) is a key component for bidirectional data traffics applied for optical communication. Up to date various types of Muxer/Demuxer have been proposed and demonstrated. A grating coupler diffracts light into substrates or waveguides, along which light beam propagates by total internal reflection. In addition, one can exploit the dispersive and filtering characteristics of gratings, for dropping or separating one or several wavelengths from one another. When a laser beam containing two wavelengths is striking the surface of the grating with an incident angle within certain range, four diffracted beams will be generated. If two diffracted beams, corresponding to different wavelengths, meet the condition of total internal reflection, they will propagate inside the glass substrate (performs as a waveguide). While the third one cannot meet total reflection condition, and the last one should become the evanescent wave. Therefore it can separate two signals and couple signals to different waveguides. These functions are suited for WDM application and directional couplers. For convenience sake, the visible lights at 458nm and 633nm were used as the incident laser beams. To give a simple sample for 1×2 demultiplexing system, a holographic grating was recorded, with the period around 441nm which was chose discretionally within the certain range. The primary experimental results indicate that the two-wavelength signal can be separated and coupled into the respective waveguide as long as the grating is recorded and operated complying with the certain condition. The average insertion loss and crosstalk of the device were presented in this paper.

Small-angle beam deviation has many applications and is conventionally performed by wedge prisms. The usual method suffers from a disadvantage that the manufacturing tolerances limit the resolution to about an arc second. The paper presents a new technique of using low frequency gratings to realize small-angle beam deviation with higher resolution. By rotating a grating placed in the laser beam path, the deviation of the diffracted light beams can be controlled. Using the proposed method, very small beam deviation angle can be achieved under large grating rotation angle, resulting in high reduction ratio. Theoretical analysis shows that as long as the grating period is large enough, the reduction ratio can be much higher than that given by a wedge prism. The theoretical result has been verified experimentally using a holographic grating with 7.25 μm period placed in a Mach-Zehnder interferometer.

The one-dimensional Non-local Photo-Polymerization Driven Diffusion (NPDD) model, which governs the temporal evolution of holographic grating formation in photopolymers, has been further developed to include all major photochemical processes. These effects include: i) non-steady state kinetics, ii) spatially non-local polymer chain growth, iii) time varying photon absorption, iv) diffusion controlled effects, v) multiple termination mechanisms, vi) inhibition, and vii) post-exposure or dark-reaction effects. The resulting analytic expressions for the monomer and polymer concentrations are then derived and their validity tested against experimental data using a 4-harmonic, numerical fitting regime. The temporal variation in the refractive index modulation is accounted for using the Lorentz- Lorenz relation, and the effects of dark reactions for short holographic exposures are examined for a range of photopolymer materials.

Highly efficient volume reflective, dynamical holographic gratings in doped Ti₁₂TiO₂₀ crystals have been observed. We demonstrated doped Ti₁₂TiO₂₀ single, electro-optical crystal and experimental set up, which combines high reversibility, small response time, high diffraction efficiency and practically unlimited number of cycles hologram recording, readout and erasing. It allows using doped Ti₁₂TiO₂₀ crystal as an attractive diffractive optical element in Dynamical Holographic Sensor -DHS for metrology applications. The high image contrast of the real time dynamical holographic interferograms without application of external electric field has been obtained for non transparent diffuse reflective objects using commercial available CW He-Ne laser. DHS applications for nondestructive test of the most vital parts engineering constructions to prevent premature failure have has been demonstrated. DHS application for visualization of cryogenic fields in the near zone of cryoultrasonic cancer tissue destructor has been presented.

In order to further improve photopolymer materials for applications such as data storage, a deeper understanding of the photochemical mechanisms which are present during the formation of holographic gratings has become ever more crucial. This is especially true of the photoinitiation processes, since holographic data storage requires multiple sequential short exposures. Previously, models describing for the temporal variation of the photosensitizer concentration as a function of exposure have been presented and applied to two different types of photosensitizer, which includes the effects of photosensitizer recovery and bleaching under certain conditions. In this paper, based on a detailed study of the photochemical reactions, the previous model is improved to more closely represent these physical effects in a more general fashion, enabling a more accurate description of the time varying absorption and thus of the generation of primary radicals.

Photopolymer materials are practical materials for use as holographic recording media as they are cheap and maintain high diffraction efficiencies at low noise level. Applications such as holographic data storage require large thickness in order to enable outstanding performance and store many pages of information in small angular steps recorded within the same volume. Such holographic gratings can be recorded by rotating the material sample peristrophically with respect to the recording beams or by altering one or both the incident angles of the recording beams. This results in gratings, which in general having a slanted geometry. Despite the physical significance of the slanted holographic gratings, most of the research presented in literature is based on the simplified unslanted recording geometry. A physically accurate electromagnetic representation of the slanted holographic gratings recorded in photopolymers is necessary in order to extract key material parameters. In this paper we present a model based on a set of two coupled differential equations, which include the effects of: (i) An exponential decay of refractive index modulation in the direction of the beam propagation due to the variation of absorption with depth; and (ii) A linear variation in the spatial period of the grating (i.e. chirp). Numerical and approximate analytical solutions of this model are found. The model is applied to analyze the experimental data in order to extract key volume grating and photopolymer material parameters.

The results of investigations of kinetics of photoanisotropy induction and relaxation in polarization-sensitive media with conformation-orientation mechanism of the anisotropy induction having significant dark relaxation are presented. It is shown that such materials can be applied for tasks of dynamic polarization holography. With the purpose of improvement dynamic characteristics of polarization-sensitive materials azodye Nitrodimethyl red (NDMR) is specially synthesized. Materials on the basis of NDMR are used for recording dynamic polarization-holographic gratings with different profile of anisotropy. The results of the investigation of kinetics of diffraction efficiency (DE) of these gratings and the analysis of polarization state of diffracted orders are given. It is shown that time of a cycle of recording/erasing for gratings of some types is of the order of 100 ms at DE = 21 %. The theoretical model of dynamic polarizationholographic recording on such materials is presented. Possible applications of the methods of dynamic polarization holography are discussed.

In this paper we present results of theoretical and experimental research of dynamic holographic system based on optically-addressed liquid crystal light modulator inside optical feedback loop, which provides asymmetrization of grating's profile. We use computer-based signal loop instead of pure optical link. This approach gives us solution for hysteresis problems and significantly reduces optical scheme complexity.

We are studying electronic holography and have already developed a real-time color holography system for live scene which includes three functional blocks, capture block, processing block, and display block. One of the issues of such systems is to spoil half of the captured 3-D information due to half-zone-plate processing in processing block, which means the resolution of reconstructed 3-D objects is reduced to half at the instant of processing block. This issue belongs to not only our system but also all similar systems, because electronic display devices do not have enough resolution for hologram even now. In this paper, we propose to use semi-lens lens array (SLLA) in capture block to solve this issue, whose optical axis of elemental lens is not at the center of elemental lens but at the edge of it. In addition to that, we will describe the processing block for SLLA. We show the basic experimental results that SLLA is better than general lens array.

We have been developing the projection type display system[1]. In the case of projection type display, it needs to use the screen in order to project the image clearly. We could get the wide viewing area using the mist screen[2-4]. However, the image with mist screen was flickered by gravity and air flow. Then we considered to reduce the flicker of the image and we found that flicker can be reduced and viewing angle became more large. This time we report the large viewing angle projection type display system using screen made up with very small particle size smoke and flow controlled nozzle. Hence, at first we considered the most suitable particle for the screen and then the shape of screen and then we constructed the array of flow controlled smoke screen. By the results of experiment we could get considerably high contrast flicker-less image and get the viewing angle more than 60° by this flow controlled nozzle attached new type smoke screen and moreover we can get the walk through type display with this method and make clear the efficiency of this method.

Invariant correlation filters application allows to achieve correlation peak invariance in the presence of distortions of input object in comparison with reference object. One of the most perspective correlation filters are Linear Phase Coefficient Composite Filters (LPCC filter). These filters provide good recognition results in the case of geometrically distorted contoured binary input objects. LPCC filter realization in 4-f correlator demands formation of corresponding impulse response of the optical system. The results of synthesis and realization of LPCC filters as holographic diffraction elements are presented in the paper.

The construction of a write-once-read-many-type optical write-read-head for volume holographic data storage in disk-based photopolymer storage media is discussed. Its design is based on the photonic integration concept called planar-integrated free-space optics. A proof-of-principle demonstrator was fabricated, it contains a 3mm thick fused silica wafer that carries most passive components for the reference and the signal beam relay in the form of diffractive optical elements, a translucent liquid crystal microdisplay, and the CCD sensor of a webcam. Phenanthrenequinone-doped polymethylmethacrylate was chosen as storage material, a DPSS laser with λ = 532nm serves as light source. We report about preliminary experiments to determine suitable exposure parameters for holographic write-read operations, and on the use of data matrix codes for the encoding and decoding of information.

Digital holography is one of the most promising tool for industrial applications. Over a period of years a number of effective compensating techniques have been developed. In this paper compensation and comparative techniques will be summarized to develop more intelligent measuring systems. Digital holography is an excellent tool for comparative measurement. Using this technique remote measurement is also can be done, because the real or simulated digital holograms of the master object can be transferred via Internet. We present a new measurement setup, combining two out-of-plane displacement measurements with different sensitivities and an adaptive compensation method. Using this method we can produce much more precise displacement map, than it would be possible by a single measurement.

Recording and real time reconstruction of digital hologram sequences have recently become feasible. The amount of information that such hologram sequences contain results in voluminous data files, rendering their storage and transmission impractical. As a result, compression of digital hologram sequences is of utmost importance for practical applications of hologram sequences. In the absence of a specific hologram sequence compression technique, a first concern is how a high-performance conventional video compression technique would perform. Such a technique would not be optimized for hologram sequences but would provide a threshold that all hologram sequence compression techniques should reach. In this paper, the use of MPEG-4 part 2 video coding algorithm for the compression of hologram sequences is investigated. Although the algorithm was originally developed for the compression of ordinary video, we apply it on digital hologram sequences and investigate its performance. For this, appropriate digital hologram sequences are used to asses how the coding algorithm affects their information content. In addition, we investigate whether MPEG-4 interframe coding, which aims to achieve compression by exploiting similarities across adjacent frames of the sequence, offers any advantage compared to intraframe coding, where each frame is coded independently. Results show that the MPEG-4 coding algorithm can successfully compress hologram sequences to compression rates of ~ 20 : 1 while retaining the reconstruction quality of the hologram sequences.

Fabricating 2-dimensional (2D) photonic crystals (PCs) on InSnO2 (ITO) layers of LEDs can largely enhance light extraction efficiency. The paper presents the theoretical analysis for determining the optimal lattice constants for PC-LEDs to acquire more efficient light extraction. The equations for obtaining optimal hexagonal lattice constants corresponding to different LED wavelengths were derived. Calculation shows that for 450 nm GaN-LEDs, the optimal lattice constant is about 500 nm, and for the lattice constants in the range from a few micron to 500 nm, light extraction increases with the reduction of lattice constant. In the experiment, hexagonal PCs with 1.8 micron, 1.5micron and 1.2 micron lattice constants were fabricated in ITO layers of GaN-LEDs using holographic 3-beam interference approach and wet etching, resulting in 6%, 12% and 22.5% output increase respectively under 20 mA current injection. The experimental result demonstrates that higher light extraction is acquired with the lattice constants closer to the optimum, which is consistent with the theoretical analysis.

This work presents the working principle for digital holography with arbitrary phase-step reconstruction using multiple holograms. The arbitrary phase-step of the reference wave can be easily estimated with two different approaches -blind searching algorithm (Meng et al.) and the limited area algorithm (Hsieh et al.). Using these approximations, the magnitude-contrast images are reconstructed without dc term and twin-image blurring, but the phase-contrast images are filled with phase distortion. Computer simulations are carried out to verify the proposed approach and optical experiments are performed to validate it. The optical results and spatial resolutions using different estimation of the phase-step are presented and discussed herein.

A single-exposure holographic technique for fabricating 2-dimensional photonic crystals (PCs) with hexagonal lattices is presented. A specially made holographic optical element (HOE), which consists of three holographic gratings, is used to generate three interference beams simultaneously under the illumination of a single laser beam. Theoretical analysis indicates that by selecting appropriate grating period and illuminating wavelength, the hexagonal lattice patterns formed by the interference of the three beams can have the lattice constants in the range from micron to sub-micron. Moreover, to obtain uniform lattice pattern with high contrast, the gratings in the HOE must have proper grating shape and depth. In the experiment, hexagonal lattices with lattice constants from 5 μm to 620 nm were fabricated in photoresist using the method. The patterned photoresist layers can be used as the masks to generate PCs in semiconductor materials through dry or wet etchings.

In holographic recording photopolymers the diffraction efficiency develops according to Kogelnik expression during hologram recording stage. In the ideal situation, the curve of diffraction efficiency versus energetic exposure has a linear zone, although it is usual to find examples of deviations to this behavior. In this investigation we study different cases in which there are deviations to ideal behavior, proposing different hypothesis in order to explain the situations that can be experimentally obtained. The more important deviation experimentally observed is when the first maximum is lower than the second one in the diffraction efficiency versus exposure curve during recording. A main hypothesis is presented, which is related to the dye concentration into the layer and the molecular weight of the polymer chains generated in the polymerization process.

The new modified holograms multiplexing method using normal to holographic recording media reference beam incidence and off-normal signal beams incidence is offered for application in holographic memory system having high information capacity and high data rate. Signal beams are located around reference beam concentrically. In this case quantity of multiplex holograms in the same area of recording media is equal to quantity of signal beams. Experimental holographic memory system model applying offered method is tested. Possibility of multichannel optical head application for data recording and retrieving is shown. Offered multiplexing method advantages consist in following: obviating of the necessity of recording media rotation; crosstalk noise free restored data page images; possibility of thin holographic recording media application.

Holographic fabrication methods of regular and nonregular relief-phase structures on silver-halide photographic emulsions are considered. Methods of gelatin photodestruction under short-wave ultra-violet radiation and chemical hardening with the help of dichromated solutions were used as a technique for surface relief formation. The developed techniques permitted us to study specimens of holographic diffusers and microlens rasters with small absorption and high light efficiency.

The paper presents the investigation on the anti-reflection property of 2-dimensional periodic structures on silicon surface for high efficiency solar cells. The characteristics of micron-to-submicron periodic surface-relief structures for broadband anti-reflection silicon layers are studied theoretically and experimentally. Theoretical analysis is carried out to determine the appropriate sturcture period. Hexagonal and cross grating structures were fabricated on the surfaces of silicon wafers using hologrpahic and wet etching techniques. Measurement on the silicon wafers with fabricated structures shows significant reduction of surface reflection for the wavelength from 300 nm to 1100 nm.

In this paper, a transmitting process of a sequence of holograms describing 3D moving objects over the communicating wireless-network system is presented. A sequence of holograms involves holograms is transformed into a bit stream data, and then it is transmitted over the wireless LAN and Bluetooth. It is shown that applying this technique, holographic data of 3D moving object is transmitted in high quality and a relatively good reconstruction of holographic images is performed.

We propose a new technique for retrieving color information. The color data taken by a digital camera is transferred to two-dimensional data on the color chart and displayed on a spatial light modulator. This modulation technique is combined with a retrieval technique using a joint transform correlator. The color data, e.g., photograph of a flower, are retrieved by this system, and the same color data (photograph) can be perfectly selected from the many reference data. This technique will open a new area of retrieval techniques for ambiguous images based on shape and color information.

Holographic data storage is a new optical technology which allows an important number of bits to be stored in a recording material. In this work, holographic data pages were stored in a PVA/acrylamide photopolymer layer using a peristrophic multiplexing method. This material is formed of acrylamide photopolymers, which are considered interesting materials for recording holographic memories. A liquid crystal (LCD) device was used to modify the object beam and store the data pages in the material. This LCD was used to modulate the object beam in order to reduce the zero frequency of the Fourier Transform (FT) of the object. The scheme used to reduce this frequency was hybrid ternary modulation (HTM).

High spatial-frequency fringes associated with reflection HOEs are difficult to obtain with currently available recording materials. In this work holographic reflection gratings were stored in a PVA/acrylamide photopolymer. This material is formed of acrylamide photopolymer which is considered interesting material for optical storage applications such as holographic memories. The experimental procedure for examining the high spatial frequency response of this material is explained and the experimental results obtained are presented. With the aim of obtaining the best results, the performance of different material compositions is compared.

For holographic memory, write-once type data recording has been studied by using photopolymer material. By considering the fact that the development of optical disks has been undertaken for both the ROM type and recordable type, there seems to exist a need to develop a ROM type disk for holographic memory. For this ROM type disk, the desired manufacturing method will be the one used for DVD disk production. Also, from the view point of data transfer speed, the function to reproduce data from a disk continuously rotating at high speed seems necessary. This paper describes a phase code multiplexed ROM type holographic memory using computer generated hologram as recorded data.

Polyvinyl/acrylamide (PVA/AA) photopolymers are often used as holographic recording materials. Depending on each particular application, different spatial frequencies can be recorded. The only limitation appears when high spatial frequencies are stored (over 2500 lines/mm the diffraction efficiencies achieved are very low). This cut-off spatial frequency is due to the finite size of polymer chains. On the other hand, in the case of very low spatial frequencies, monomer diffusion times are highly increased and so there are important distortions in the shape of the gratings stored. In order to characterize the hologram formation in these types of materials, many parameters must be taken into account. One of the most important parameters to measure is the diffusion of the molecules inside the layer. In this sense, when very low spatial frequencies are recorded, component diffusion and thickness variations can be determined more accurately. In previous works, we have characterized the photopolymer at the zero spatial frequency limit, where diffusion does not take place, measuring the refractive index variations and the shrinkage. In this work we have recorded different long period gratings (at very low spatial frequencies diffusion starts to be important) and we have analyzed the profiles formed in the material during exposure and the refractive index distributions. This study has been carried out measuring the transmission and reflection orders of diffractive gratings. Furthermore, to obtain a deeper insight into the profile of the gratings recorded and especially into the sharpness of their edges, we have obtained numerically the diffraction-efficiency values fitting a Fermi-Dirac function to each profile.

We demonstrate implementation and performance of microdisplay systems based on liquid-crystal technology in a variety of applications in holographic mastering. These displays can encode 2D objects information in grey scale or address holographic patterns in amplitude or phase. The main advantage is here to address any content dynamically with typically 60 Hz. Furthermore they show a resolution up to 1920×1200 pixels with a pixel size as small as 6.4 microns. Therefore they are extremely suitable for a dynamic or multi-exposure mastering process, to incorporate image content, phase-encode objects or any holographic features. This technology is already being used in holographic security applications as well as in commercial and display holography. We report about a few applications/implementations and show experimental results and performance parameters.

Various photopolymer materials have recently found a significant number of useful applications in microelectronics and the PC board industries. Some of these materials have also become attractive optical recording materials for the recording of holographic devices such as diffractive optical elements and gratings, or as data storage media, for the fabrication of optical waveguides and photonic processing structures. Ever increasing requirements, driven by application developments, has lead to the rapid development of newer generations of such materials. As the ever increasing number of new materials is developed and used, there is a need to characterize the material behavior pre-and post exposure. In order to produce materials with a desired set of material properties one has to understand the photochemical processes present during recording. Although in most case emphasis is placed on studying the high spatial frequency response and the related limitations of such materials, the low spatial frequency response characteristics can also supply useful information regarding the processes taking place during grating formation. In this paper we present the experimental results obtained following a detailed examination of the low spatial frequency response of a photopolymer material in the case of exposure at different recording intensities. The time dependence of the diffraction efficiency of the grating must be then analyzed using the appropriate diffraction theory of phase gratings. Furthermore the results of examining the angular scans of the resulting grating diffraction efficiency are presented in order to specify the condition of the diffraction regime (e.g. thin, thick) for such low spatial frequency gratings.