The subject today known as holography emerged from research in three diverse locations and having distinct origins, aims and methods: at a commercial electrical laboratory in Rugby, England, from the late 1940s until the mid 1950s; at the Vavilov State Optical Institute in Leningrad from the late 1950s and again from the mid 1960s; and, from a classified research laboratory operated by the University of Michigan beginning in the mid 1950s and accelerating from the early 1960s. The scientists, engineers, artisans, entrepreneurs and companies in that third location dominated the subject through the 1960s, making Ann Arbor, for a time, the 'holography capital of the world'. Based on extensive unpublished documents, artifacts and interviews with some two-dozen participants (much of it as yet unavailable in publicly accessible archives), this paper focuses on the origins of the subject in Ann Arbor, Michigan. It also explores how the initial explosion of interest was transmitted to other research groups, firms, artists and the wider public.

The COST action P8 has been initiated by a group of European Scientist and receives funding by the European Science Foundation ESF starting in March 2002 for four years. The action promotes cooperation between researchers from many European countries by organizing worhshops, conferences and short term scientific missions. Information about the conference activities can be obtained from the Action Web site: http://moebius.physik.tu-berlin.de/lasergrp/COST_P8/index_ns.html

A comparative investigation of the photochemical behavior of dichromated gelatin (DCG), dichromated polyacrylic acid (DCPAA) and dichromated polyvinylalcohol (DCPVA) gave evidence for the similarity of the photochemical behaviour involved when recording holograms in DCG and DCPVA. Chromium (V), the chromium species resulting from the photoredox process between the starting chromium (VI) (dichromate) and the polymeric chain, was stable likely strongly complexed in gelatine and polyvinylalcohol. The quantum yields of the reaction are high and similar for both reactions. On the contrary, even though chromium (V) was also formed during the primary process in DCPAA, this species was quite unstable and disappeared as soon as the irradiation was stopped. The behavior observed in DCG can be assigned to the presence of OH groups on the polymeric chain, these groups being the only groups present in polyvinylalcohol. Actually, the stability and the state of complexation of the different chromium species was completely opposite in the two matrices: the stabilization of chromium (V) resulting from the photochemical charge transfer in DCPVA, by complexation with PVA is in contrast to what was observed in DCPAA where chromium (V) was highly instable. Regarding chromium (III), the final reduction chromium species, it was complexed in PAA and not in PVA. The experiments performed on films of DC (PVA+PAA) with only a few percents of PAA gave evidence for the strong influence of the presence of the carboxylic groups on the photochemical behavior: the rate of the formation and the stability of chromium species that reflects the chelating properties of the polymeric matrix. The photochemical results were correlated to the results obtained when recording holograms in the corresponding material: a very nice agreement appeared between the two sets of results. An innovative approach combining the monitoring of the structural modification of the polymeric matrix and the fate of the various chromium species ((VI), (V) and (III)) was then implemented. For the first time, it was established that chromium (V) was at the origin of the cross-linking implied in the hologram formation by acting as a bridge between hydroxyl groups of the polymeric chains. A second unanswered question was also elucidated. The improvement brought by ammonium dichromate with respect to potassium dichromate involves amide groups as additional chelating sites for chromium (V) resulting in the increase of the matrix cross-linking.

In this paper we report on holographic diffraction gratings recorded at visible light wavelength, which can be probed at telecommunication wavelengths. The recording material is an easily prepared, self-processing photopolymer, all of whose components are water soluble. Transmission gratings of various types, namely unslanted, slanted, totally internally reflecting and Bragg gratings were all fabricated. Diffraction efficiencies at telecommunications wavelengths compare favourably with those obtained in visible light.

In our most recent study diffusion constants were measured in the simplified monoacrylamide version of a dry acrylamide based photopolymer holographic recording material developed in the Centre for Industrial and Engineering Optics. In this paper we report diffusion constants for the commonly used photopolymer formulation, which also contains the crosslinker bisacrylamide. A physical model for the recording mechanism is proposed which explains the two way diffusion observed in both systems, and is in agreement with much of the previously observed behaviour of the material, particularly in regard to dependence of diffraction efficiency growth on spatial frequency and persistence of holographic gratings under uniform exposure. The model is also supported by direct observation, under a surface profiler, of the boundary between an illuminated and un-illuminated area at the photopolymer surface.

A nanoparticle-doped acrylic photopolymer is characterised as a material for holographic recording. The influence of nanoparticles on the photopolymer dynamic range, dynamics of recording, temporal stability and mechanical stability in terms of shrinkage has been studied. The dynamics of recording and the temporal stability are investigated by real time monitoring of the build up of diffraction gratings of spatial frequencies of 200 to 2000 1/mm. The shrinkage has been characterised by recording slanted transmission gratings and observation of the change in the Bragg angle.

The Nonlocal Polymer Driven Diffusion (NPDD) model successfully predicts high spatial frequency cut-off and higher harmonic generation, experimentally evident in holographic gratings recorded in free radical chain photopolymer materials. In this paper the NPDD model is extended to include a nonlocal material temporal response. Previously it was assumed that following a brief transient period, the spatial effect of chain growth was instantaneous. However, where the use of short exposures is necessary, as in optical data storage, temporal effects become more significant. Assuming that the effect of past chain initiations will have less effect on monomer concentration at a later point in time than current initiations, a normalized exponential function is proposed to describe the process. The extended diffusion model is then solved using a Finite-Difference Time-Domain technique to predict the evolution of the monomer and polymer concentrations during and after grating recording. The Lorentz-Lorenz relation is used to determine the corresponding refractive index modulation and The Rigorous Coupled Wave Method applied to determine and/or process diffraction efficiencies. A fitting technique is then used which first solves the diffusion model as described and determines a set of parameters which give best fits to the experimental data. Results show that the inclusion of the nonlocal temporal response is necessary to accurately describe grating evolution for short exposures i.e. continued polymer chain growth for some period after recording resulting in an increase in the refractive index modulation. Monomer diffusion is also shown to influence refractive index modulation post-exposure. Monomer diffusion rates determined to be of the order of D ~ 10^-11 cm²/s and the time constant of the nonlocal material temporal response function being of the order of τ_n ~ 10^-2s.

We investigate different types of ferroelectric photorefractive Sn₂P₂S₆ at different wavelengths in the red and infrared. We show that modifying the growth conditions and doping with Te can efficiently improve the photorefractive properties of Sn₂P₂S₆. Photorefractive two-beam coupling gain increases for Te-doped Sn₂P₂S₆, up to 17 cm^-1 at a wavelength of 633 nm and up to 7 cm^-1 at 860 nm, compared to conventional "yellow" Sn₂P₂S₆ which has a gain of 4-7 cm^-1 at 633 nm and 2 cm^-1 at 860 nm. We demonstrate self-pumped phase conjugation in ring cavity scheme at 780 nm for Te-doped Sn₂P₂S₆ with a reflectivity of up to 30% in a relatively short rise time of less than 50 ms for 2 W/cm² pump intensity.

A method, based on phase-contrast and interference microscopy, was developed for direct microscopic observation of temporal evolution of phase holograms in photorefractive crystals. Interference microscopy was adapted to the study of photorefractive holograms. First a hologram was recorded in the sample, and diffraction efficiency was monitored during hologram build-up using inactinic laser light. Thus kinetics of hologram build-up could be determined. The initial hologram was erased using white light. Then a series of write-erase cycles were performed with increasing exposure times up to an exposure corresponding to saturation of the grating. Holograms were observed by interference microscope after each exposure. The time elapsed between the exposure and the microscopic observation was negligible compared to the relaxation time of the hologram. The obtained temporal evolution of grating profile gives a deeper insight into the physical mechanism of hologram formation in photorefractive materials than diffraction efficiency measurements. Congruently grown samples of LiNbO₃: Fe, with Fe concentrations in melting of 10^-3 were studied by the above method. Sample thickness was set to 300 μm to allow correct microscopic observation. Plane-wave holograms were recorded in the samples using an Ar-ion laser at λ=514 nm of grating constants of 3.3 and 7.0 μm.

Interband photorefractive gratings induced by deep ultraviolet light at λ_UV = 257 nm are investigated in pure and Mg-doped near-stoichiometric LiTaO₃. By controlling the stoichiometry, the response time and dynamic range of the interband photorefractive effect can be very much improved. Measured time constants are in the order of a few tens of milliseconds for UV light intensities of about 100 mW/cm². Further, we report that Mg doping of near-stoichiometric LiTaO₃ increases the grating response rate by a factor of 50 compared with the one in undoped crystals. In Mg-doped near-stoichiometric LiTaO₃, quasi-fixing of holographic gratings with UV light and nondestructive readout in the visible has been observed. These quasi-fixed gratings are written in the deep traps of the crystal.

Research dealing with models to predict and understand the behaviour of photopolymers have generated many interesting studies considering a 2-dimensional geometry. These models suppose that the photopolymer layer is homogeneous in depth. Using this approximation good results can be obtained if the thickness of photopolymers is less than 200 μm. However, it is well known that Lambert-Beer's law predicts an exponential decay of the light inside the material. In recent years intensive efforts have been made to develop new holographic memories based on photopolymers. For this application the thickness of the layer is increased, usually to more than 500 μm, and Lambert-Beer's law plays a significant role in the recording step. The attenuation of the index profile inside these materials has been measured, showing that it is an important phenomenon. This attenuation limits the maximum effective optical thickness of the grating and shows that the 2-D models can not be applied in these cases. For this reason in this work a 3-dimensional model is presented to analyze the real behaviour of the photopolymers and study the variations in the index profile in depth. In this work we examine the predictions of the model in the case of a general dependence of the polymerisation rate with respect to the intensity pattern, and the effects of varying the exposure intensity are also compared in 3-D cases. Finally, the limitation of the data storage capacity of the materials due to the Lambert-Beer law is evaluated.

The investigation of the casting and properties of the holographic photopolymer material in hybrid organic-inorganic binder with thickness 0.4-1 mm is described. The hybrid matrix formation was carried out by synthesis of N-vinylpyrrolidone vyniltriethoxysilane co-polymer and subsequent hydrolytic condensation of this co-polymer with tetraethoxysilane pre-sol. It is shown the possibility of formation of stable to crack the solid volume hybrid matrix at ratio pre-sol:co-polymer 1:4. Recording of transient and reflection holograms in hybrid 0.46 mm thickness photopolymer material was carried out. Angle selectivity of the transient hologram was 0.17° and shrinkage of material, measured by changing of Bragg condition of transient hologram didn't exceed 0.7%. The obtained holographic properties were improved on the order of value in comparison with photopolymer material in organic polymer binder.

Experimental investigation and modeling of angular and spectral selectivity of volume transmission and reflection holograms in PVA/acrylamide photopolymer has been carried out. Influence of non-uniform light absorption, shrinkage of material thickness, changing of the average refractive index and refractive index modulation through the hologram thickness, and bending of interference fringes are taken into account.

Dynamics of pulse holographic recording of diffraction gratings has been studied in photopolymer material: polyvinyl alcohol (binder), acrylamide (monomer), Erythrosine (dye-sensitizer), triethanolamine (donor-initiator). Pulse duration of the 2nd harmonic of Nd:YAG laser is 10 ns. A formation of polymer (permanent) and primary gratings were observed after pulse. Photopolymer composition optimization has been provided within conditions of pulse recording. Kinetics models of photopolymer formation subject to radical death due to recombination and purity have been compared with experimental data.

The possibility and features of the holographic recording by excitation of the forbidden singlet-triplet transitions are considered in the report. The experimental demonstration of the hologram recording on forbidden transition is carried out in thick photopolymer material sensitized by Erithrozine dye. The single hologram with diffraction efficiency DE=50% and 16 angle multiplexing hologram were recorded by irradiation of the low intensity He-Ne laser (632 nm) at high concentration of the sensitizing dye and at high optical density in allowed absorption band of dye. The growth of DE of transition hologram depending on the Kr+(647 nm) laser irradiation intensity of was studied. The observed linear dependence of the maximal rate of DE growth on the intensity of recording irradiation was explained by two steps-two photon excitation (T₁←S₀, T₂←T₁) of the dye in the photopolymer samples.

The aim of this work is to understand the effects of the shrinkage phenomenon in H-PDLC reflection gratings through the realtime analysis of their transmission spectra during the recording process. The realtime spectroscopic analysis of the samples showed a light intensity dependent free-radical polymerization indicated by a quick growth of the reflection peak whose corresponding diffraction efficiency, measured at normal incidence, is in the range of 40%-45% depending on the photopolymerization conditions. An optical shrinkage corresponding to a 4.3% displacement of the reflected wavelength from the expected value has been detected. This value of the shrinkage is in agreement to that mesaured in a similar system.

Refractive data for more than fifteen types of American, German and Japanese optical polymers at laser emission wavelengths in the visible and near-infrared spectral regions from 406.7 nm (Krypton) to 1080 nm (Nd:YAP) is presented. We have measured the refractive indices of the examined optical plastics (OPs) at selected wavelengths from 435.8 nm to 1052 nm with an accuracy of ±0.001. Laser measurements at HeNe emission wavelength λ=632.8 nm have been also accomplished. A modified Caushy's dispersion formula for computer modelling of the refractive characteristics of OPs in the region of normal dispersion is utilized. On its basis a new OptiColor program is realized for determination of the dispersion coefficients and dispersion curves of any optical material. The obtained data for the OPs' dispersion coefficients, refractive indices at laser emission wavelengths, and dispersion charts could be useful for the optical designers and production technologists of laser devices.

This study investigates the optical characteristics of biopolymer films from gelatin, mannan and glucomannan. Glucomannan was produced from the yeast strain Sporobolomyces salmonicolor, isolated from lichem samples from the region of the Bulgarian Base on Jirings for Island, Antarctica. Transmission spectra of gelatin, mannan and glucomarinan in the visible, NIR and JR region of the electromagnetic spectrum have been taken. The refraction indices of biopolymer water solutions studied and of the films obtained from them for two wavelengths have been measured. The dispersion coefficients of Sellmeier of the film and the liquid phase of the given polymers have been calculated. The temperature dependence of refraction index of the given polymers has been studied by means of Refractometer Abbe.

Synthesis of diazocarbazole dyes is described together with their photoisomerizaton properties that were demonstrated under strong illumination with a laser beam. It was shown that the dyes could be used as precursors to synthesis of carbazole based polymers suitable for applications in photonics.

Novel acrylate copolymer with carbazole pendant groups and derivatives of bipyridine as side chains were synthesized, in which derivatives of bipyridine as electro-optic chromophores and carbazolyl as photoconductive moiety were covalently linked on the acrylate backbone. 2-{9-Carbazolyl)ethyl methacrylate (CEM) and 2-methyl-acrylic acid 2-{4,4'-dimethyl-5'-[2-(5-methyl-thiophen-2-yl)-vinyl]-[2,2']bipyridinyl-5-yl}-ethyl ester (BiPy) were synthesized and then copolymerized to give (99:1), (98:2), and (92:8 mol/mol) CEM/BiPy copolymers. Solutions of the copolymers in dioxane were examined for their photoluminescence properties.

Optical storage in azobenzene-containing polymers is based on the alignment of the polymer chains initiated by the reorientation and ordering of the azobenzene groups. This process requires considerably high recording energies. We investigate photoinduced birefringence in two types of acrylic cyan-azo polymers - one amorphous and one liquid crystalline. We show that for both types the light energy required for the recording can be reduced by an order of magnitude if the photoalignment is done at elevated temperatures. The optimal temperatures depend on the polymer. In our case they are 52-55°C for the liquid-crystalline polymer and 50-60°C for the amorphous polymer. At these temperatures birefringence as high as 0.07 can be obtained at light intensities 30-40mW/cm² for about 100s and these values are retained after cooling the polymer films.

The photoinduced processes in four methacrylic azobenzene-containing copolymers have been investigated. The materials have been synthesized by radical type polymerization of the chromophore monomer and methylmethacrylate. The copolymers differ only in the concentration of chromophore monomers (P1 - 5mol%, P2 - 23mol%, P3 - 5Omol% and P4 - 100mol%). The first three polymers are amorphous and the fourth (P4) is liquid-crystalline. We have established that the photoequilibrium concentration of cis-azobenzenes obtained on irradiation with nonpolarized UV light and with a linearly polarized Ar beam decreases with increasing concentration of chromophore monomers: it is highest for polymer P1 and lowest for P4. Similarly, values for the observed dichroism induced by polarized light can be linked to chromophore concentration. But here lower values of the concentration of chromophores correspond to lower values for photodichroism. This, however, does not hold for the P4 polymer and this is most probably caused by its liquid-crystalline properties.

Experimental studies on the erasure effect of thermal neutron irradiation on elementary photorefractive hologram in LiNbO₃:Fe single crystals are reported. This phenomenon results from the large effective cross-section of ⁶Li for thermal neutrons and from the large number of the electrons excited to the conduction band by the kinetic energy that is released during the neutron generated α-decay of ⁶Li nuclei. The excited electrons decrease the electric space-charge field of the previously recorded holographic grating and decrease its diffraction efficiency. The sensitivity threshold of the effect is better than 53 mSv (4×10⁹ cm^-2 fluence) at neutron energy of 0. 17 eV. Discussion of potential application ofthe phenomenon is also given.

Bismuth germanate Bi₄Ge₃O₁₂ (BGO) single crystals doped with ruthenium, manganese and ruthenium plus manganese are grown by Czohralski technique with automatically diameter-weight control method. The effect of doping on the light-induced, magneto-optical and holographic properties of BGO single crystals is studied. It was found that the optical transmission spectrum of doped samples is modified strongly under thermal annealing and homogeneous illumination with UV light as well as the photochromic effect is fully reversible. The magneto-optical rotation was measured and Verdet constant was calculated at visible spectral range. Holographic grating are successfully recorded at 633 nm.

A review of the high-resolution VRP Silver Halide photo-materials (available through the Geola international distribution network) is presented. In addition to traditional holographic applications, the behaviour of current VRP materials is discussed in relation to embossed mastering origination, masks for microelectronics and X-ray tomography. Properties and applications of the fine grain, blue-green sensitive VRP plates are compared with previously available materials from other manufacturers. Recommended chemistries that may be employed with the VRP emulsion in different applications are reviewed.

It is well known that dichromated gelatin is one of the best materials for phase hologram recording. Several competing hypotheses for the nature ofthe photoinduced response in DCG have been discussed in the literature, and still there is no generally accepted point of view. Recently we have demonstrated how the optical response of DCG holograms can be analyzed on the basis of light scattering from nano-voids, which appear in the process of hologram formation. We have assumed that the voids are ellipsoids with dimensions of 10 - 40 nm, i.e. we are within the approximations of Raleigh scattering. Here, we analyze the DCG reflection hologram performance in terms of rigorous theory of light scattering with no limitations for the size of the voids. Mathematical simulations of the reflection spectra give a plausible quantitative explanation of many experimental facts related to DCG holograms obtained by the so-called 'drastic' chemical treatment after exposure.

Ultra fine grain panchromatic silver halide light sensitive material HP-P for RGB recording of reflection holograms have been recently developed. The average grain size is less than 10 nm, and recording energy for maximum diffraction efficiency for the spectral range 400-675 nm is in the frame of 0.5-2.5 mJ/cm². To estimate the life time of the new material an accelerating testing at different temperatures (40°C, 60°C and 100°C) has been applied and compared with the results for the well known red sensitized silver halide emulsions HP-650, having average grain size about 10 nm. On the base of the obtained results according Arenious low at least three months life time of the new material at ambient conditions could be guaranteed, and more than six months at -5°C storage condition.

We demonstrate a possibility to write efficient and thermally stable volume holographic gratings in a glassy polymer material based on PMMA and phenanthrenequinone with layers prepared by casting the liquid solution of ingredients on a substrate and drying to a solid state. A high concentration of phenanthrenequinone (up to 4 mol.%) makes it possible to use photosensitive layers of lower thicknesses (50 - 180 μm) for the recording of efficient holographic gratings. The exposing is followed by a thermal amplification of the grating due to diffusion of residual phenanthrenequinone molecules and fixation by an incoherent optical illumination. We present experimental temporal curves of the refractive index modulation and diffraction efficiency both under the exposure and the heating process. The behavior of the gratings under temperatures up to 140°C has been studied.

Thin chalcogenide (As-S, As-Se, Ge-Se, etc.) films find applications in many branches of modern optics: for design of optical systems operating in VIS and IR, as recording material for holographic storage, or as inorganic photoresists, etc. Very thin films are included in multi-layered CD-R and DVD structures for improvements of their performance and increase of storage capacity. That is why developments of different methods for determination of optical constants (n - refractive index, k - extinction coefficient and d - physical thickness) best adapted for concrete optical problems are still needed. Recently we have presented a method for (n, k, d) evaluation of very thin metal or semiconductor films from spectrophotometric data. Here we present investigation of the optical constants of vacuum deposited As-Se thin layers with d between 15 and 30 nm. The dispersion of the complex refractive index is studied in the spectral range of 400 - 1000 nm. The obtained results are interpreted within the frame of single oscillator Wemple-DiDomenico model. Comparison is made with data on thicker evaporated layers. We demonstrate the importance of the analysis of the uncertainties in (n, k, d) determination for the adequate choice of the film physical thickness.

The acrylamide photolymers are considered interesting materials for holographic media. They have high diffraction efficiency (ratio of the intensities of the diffracted and the incident beams), an intermediate energetic sensitivity among other materials and post-processing steps are not necessary, therefore the media is not altered. The layers of these materials, about 1 mm thick, are a suitable media for recording many diffraction gratings in the same volume of photopolymer using peristrophic multiplexing technique, with great practical importance in the field of holographic memories type WORM (write once read many). In this work we study the recording of diffraction gratings by peristrophic multiplexing with axis of rotation perpendicular to the recording media. The photopolymer is composed of acrylamide as the polymerizable monomer, triethanolamine as radical generator, yellowish eosin as sensitizer and a binder of polyvinyl alcohol. We analyze the holographic behaviour of the material during recording and reconstruction of diffraction gratings using a continuous Nd:YAG laser (532 nm) at an intensity of 5 mW/cm² as recording laser. The response of the material is monitored after recording with an He-Ne laser. We study the recording process of unslanted diffraction gratings of 1125 lines/mm. The diffraction efficiency of each hologram is seen to decrease as the number of holograms recorded increases, due to consumption of the available dynamic range, in a constant exposure scheduling. It can be seen that the photopolymer works well with high energy levels, without excessive dispersion of light by noise gratings. In order to homogenize the diffraction efficiency of each hologram we use the method proposed by Pu. This method is designed to share all or part of the avaliable dynamic range of the recording material among the holograms to be multiplexed. Using exposure schedules derived from this method we have used 3 scheduling recordings from the algorithm used. Additionaly, we use an exponential scheduling recording in order to correct the exposure times from the first iteration of the algorithm.

We demonstrate the possibility of photodimerizable chromophores attached to a short alkyl chain as a potential medium for high capacity digital optical storage. A large increase in transmission from 4% to 70% is obtained in 20 s when irradiated with a 5 mW unfocused laser beam at 257 nm in a thin film of 1-(6-Bromohexyl)uracil. Through theoretical simulations, we show that the interaction cross-section is 6 10^-18 cm² at a photon dose of 9 10¹⁶ photons cm^-2 s^-1. We also investigate the formation of holographic diffraction grating in a film, obtaining an efficiency of 16%, mainly due to a surface relief grating.

A simple, diffraction limited, optical design for a Holographic Data Storage System with a high numerical aperture and large field is presented. A system analysis is performed and the design is compared with different current and future formats for optical data storage.

Surface relief holograms are fabricated by means of irradiation of laser interference patterns. The diffraction efficiency and the surface relief depth depend on the writing energy and the polarization of the writing laser beam. The formation and erasure of photoinduced surface relief gratings (SRGs) on azobenzene-containing polymers are simulated using a numerical model based on the moving-particle semi-implicit (MPS) method. Particle motions in SRG formation and erasure are calculated and the SRG pitch and polarization dependences of the SRG growing and erasing rates are investigated. These theoretical results coincide qualitatively with our experimental results.

The nonparaxial and bidirectional beam propagation method suitable for modelling high NA near-field and holographic optical storage systems is suggested for 2D geometry and TE polarization of the incident light beam. The complex Pade approximants are introduced for correct approximation of evanescent field in the near-field optics using pole-zero shifting in the complex plane. The application of bidirectional beam propagation method to study the multimode waveguide near-field focusing system and wide-angle beam Bragg reflection from volume holographic grating is considered.

A Read-only Holographic Versatile Disc (HVD-ROM) system, using a laser diode for high capacity and high data transfer rates storage system, is proposed. With the collinear technologies' unique configuration the optical pickup can be designed as small as a DVD's, and can be placed on one side of the disc. With the HVD's special structure, the system can servo the focus/tracking and locate reading/writing address. The experiments and theoretical studies suggest that a laser diode is very suitable as a light source of our HVD-ROM system.

ROM type holographic disk that can be made by the optical disk cutting method and has compatibility with the recordable holographic memory was studied. Computer generated hologram data was recorded on the master disk by bit-by-bit recording. Then, after making a stamper, a holographic disk was made by the injection molding. To this holographic disk, it was confirmed that the data reproduction of low bit error rate is possible. In order to enable data reproduction by using a continuously rotating disk, the recorded data was made in such a way that random phase is given to the reproduced data. It became possible to distribute data to the entire area of the hologram and it enabled the reproduction of all the data of the hologram by reproducing a part of the hologram. This made it possible to reproduce data with a continuously rotating disk. Furthermore, the simulation showed that multiplex recoding became possible by the aperture multiplexing.

We present non-volatile readout of thin film polarization Fourier holograms using different wavelengths. We demonstrate application of imaged reference phase coding in portable holographic demonstrator. Experimental results approve applicability of preliminary computer simulations.

We investigate the self-induced rotation of the azimuth of light polarization ellipse in azobenzene polymers. It is initiated by the photoreorientation and ordering of the azobenzenes on illumination with elliptically polarized light resulting in the appearance of an optical axis whose direction is gradually rotated along the depth of the film. A macroscopic chiral structure is created with a pitch depending on light ellipticity and the photobirefringence ▵n in the successive layers of the film. In this work we make use of the fact that at elevated temperatures ▵n is very sensitive to light intensity. In our acrylic amorphous azobenzene polymer at temperatures 50-65°C the saturated values of ▵n are much higher for low intensity of the exciting light than for higher intensity. In this temperature range the polarization azimuth of monochromatic blue light with different intensity is rotated to a different angle after passing through the polymer film. This effect can be used for passive elements rotating the polarization azimuth depending on light intensity and for the formation of light beams with a space-variant polarization state.

Optical systems for data storage and processing of information have diffraction limited image quality. This requires an exact fulfillment of aplanatic conditions on the whole system aperture and usually leads to the introduction of two more adjacent aspherical surfaces. For exact defmition of these aspheric surface shapes it is necessary to solve numerically a system of two first-order differential equations. For this purpose, one can use Runge-Kutta or Adams-Bashforth-Moulton algorithms or combination of them both. However, solutions often can not be found, particularly for systems with high and super high numerical aperture. If the solution is not found, it is not clear whether it exists or not and what is the reason for the lack of solution. We propose an analytical solution of Wassermann-Wolf differential equations for aplanatism that overcomes such disadvantages. We show that the solution of the system of two Wassermann-Wolf first-order differential equations is mathematically equivalent to the consecutive solution of a set of independent linear equations and the most important factor of the lack of solution is the critical angle of incidence of aperture rays at the two aspherical surfaces. The proposed algorithm allows reliable and effective design of aplanatic optical systems containing two neighboring aspherical surfaces with high and super high numerical aperture and diffraction limited image quality for an object at infinity. We illustrate the successful application of the algorithm to the design of blue DVD objective with super high (0.95) numerical aperture and diffraction limited image quality.

One way to amplify the optical memory capacity is to increase simultaneously the numerical aperture of the reading and writing objective, to decrease the laser wavelength and to use optical discs with multilayer construction. In this paper we show how to optimize and design single lens aspheric objectives with high and super high numerical aperture for red and blue DVD. We demonstrate the image quality of constructions of an objective for red DVD with high numerical aperture 0.9, an objective for blue DVD with super high numerical aperture 0.95 and collimators for red and blue DVD.

We describe a technique for holographic storage by simultaneous angular multiplexing to obtain a large-scale holographic memory. We recorded 72 objects at the same time in one point on holographic plate PFG-03M from Slavich Co., using a He-Ne laser (λ = 633 nm). Each object is placed on a circular photographic transparency, separate 0.94 degree each one. The technique allows us simultaneous reconstruction of the 72 images without cross-talk. The diffraction efficiency obtained at order one is 6%. Experimental results are shown.

Digital holography is a symbiosis of physical optics and digital computers. In numerical reconstruction of optical holograms, optical wavefront is sampled, and obtained numerical data are transformed in computers for evaluating physical properties of objects that produced that wave front. In fabricating computer-generated holograms, numerical data produced by a computer are converted into a physical hologram or an optical element intended for forming real optical beams. Therefore mutual correspondence between optical transformations and their computer representations is of fundamental importance for digital holography. In the paper, this problem is addressed and different computer representations of basic optical transforms such as convolution, Fourier and Fresnel integral transforms are briefly reviewed.

Volume holography is gaining renewed interest sparked by the need for denser and faster information storage paradigms as well as for wavelength manipulation in communication networks and laser beam shaping. Conventional approaches used for theoretical analysis of the volume holographic processes are not adequate when complicated wavefronts are involved since they can only deal with elementary cases, such as plane waves. The present work exploits the fact that most holographic systems involve several waves that may propagate at large angles but each of them contains only a relatively narrow spatial frequency band. Introducing a narrow band approximation facilitates the theoretical treatment of architectures comprising several wave fronts propagating at large angles. The combination of this approximation with a generalized description of volume holography leads to a theoretical framework that is suitable for the analysis of most holographic systems encountered in the applications indicated above. A numerical study demonstrates the power of the method and the existence of a coherent motion blur that was predicted recently. The study indicates the effectiveness of volume holography for beam shaping and leads to some disturbing consequences related to bit-oriented information storage.

Digital holography has been around for over thirty years; however only in recent years has necessary and affordable recording and computing hardware become widely available. Some of the first works in digital holography are described as far back as 1966, with others following shortly after that. Today many researchers are working in this area for both application and further development of the technique. Indeed, digital holography may represent the best hope for holography as a thriving area of optics, and science. In this paper we discuss of the many applications, advantages, challenges, and opportunities that exist in the field of digital holography.

The fact that plane waves are solutions of the Helmholtz equation in free space allows us to write the exact solution to the diffraction problem as a superposition of plane waves. The solution of other related problems can also be expressed in similar forms. These forms are very well suited for directly importing various signal processing tools to diffraction related problems. Another signal processing-diffraction link is the application of novel sampling theorems and procedures in signal processing to diffraction for the purpose of more convenient and efficient discrete representation and the use of associated computational algorithms. Another noteworthy link between optics and signal processing is the fractional Fourier transform. Revisiting diffraction from a modern signal processing perspective is likely to yield both interesting viewpoints and improved techniques.

In this paper, we present an overview of some recent advances in interpolation and resampling. We are particularly interested in the linear, convolution-based interpolation techniques where new image pixels are generated by first fitting a certain continuous function to the given uniformly sampled data and then resampled at the desired coordinates. We start with stating the interpolation problem in signal and frequeny domain and then continue with describing the interpolation artifacts and how to evaluate the interpolator's performance. We then review the class of piecewise-polynomial interpolators of minimal support as the best compromise between high performance and acceptable cost. We describe efficient filter structures, discuss different optimized designs and give comparative results both experimental and analytical.

We deduce and study an analytical expression for Fresnel diffraction of a plane wave by a spiral phase plate (SPP) with an arbitrary-order phase singularity and an analytical expression for far-field diffraction of the Gaussian beam by a SSP with n-th order. The SPP was implemented as a 32-level "helical" microrelief on a low-contrast resist using an electron beam. Experiments of diffraction of the Gaussian beam by SPPs with the second-order singularity and of trapping polystyrene beads using computer-generated optical elements are discussed.

Creation of a dynamic 3-D display based on holography, in which a 3-D scene is encoded in terms of optical diffraction, transformed into the fringe patterns of the hologram that is further converted into a signal for a spatial light modulator (SLM) and displayed in real time, is an extremely challenging enterprise. There are various approaches targeted to solve associated problems.

Sequences of 2D images, taken by a single moving video receptor, can be fused to generate a 3D representation. This dynamic stereopsis exists in birds and reptiles, whereas the static binocular stereopsis is common in mammals, including humans. Most multimedia computer vision systems for stereo image capture, transmission, processing, storage and retrieval are based on the concept of binocularity. As a consequence, their main goal is to acquire, conserve and enhance pairs of 2D images able to generate a 3D visual perception in a human observer. Stereo vision in birds is based on the fusion of images captured by each eye, with previously acquired and memorized images from the same eye. The process goes on simultaneously and conjointly for both eyes and generates an almost complete all-around visual field. As a consequence, the baseline distance is no longer fixed, as in the case of binocular 3D view, but adjustable in accordance with the distance to the object of main interest, allowing a controllable depth effect. Moreover, the synthesized 3D scene can have a better resolution than each individual 2D image in the sequence. Compression of 3D scenes can be achieved, and stereo transmissions with lower bandwidth requirements can be developed.

We present novel technique for fast non-contact and continuous profile measurements of rough surfaces by use of dynamic speckles. The dynamic speckle pattern is generated when the laser beam scans the surface under study. The most impressive feature of the proposed technique is its ability to work at extremely high scanning speed of hundreds meters per second. The technique is based on the continuous frequency measurements of the light-power modulation after spatial filtering of the scattered light. The complete optical-electronic system was designed and fabricated for fast measurement of the speckles velocity, its recalculation into the distance, and further data acquisition into computer. The measured surface profile is displayed in a PC monitor in real time. The response time of the measuring system is below 1 μs. Important parameters of the system such as accuracy, range of measurements, and spatial resolution are analyzed. Limits of the spatial filtering technique used for continuous tracking of the speckle-pattern velocity are shown. Possible ways of further improvement of the measurements accuracy are demonstrated. Owing to its extremely fast operation, the proposed technique could be applied for online control of the 3D-shape of complex objects (e.g., electronic circuits) during their assembling.

Digital holography can be used to capture the whole Fresnel field from a reflective or transmissive object. Applications include imaging and display of three-dimensional (3D) objects, and encryption and pattern recognition of two-dimensional (2D) and 3D objects. Often, these optical systems employ discrete spatial light modulators (SLMs) such as liquid-crystal displays. In the 2D case, SLMs can encode the inputs and keys during encryption and decryption. For 3D processing, the SLM can be used as part of an optical reconstruction technique for 3D objects, and can also represent the key during encryption and decryption. However, discrete SLMs can represent only discrete levels of data necessitating a quantisation of continuous valued analog information. To date, many such optical systems have been proposed in the literature, yet there has been relatively little experimental evaluation of the practical performance of discrete SLMs in these systems. In this paper, we characterise conventional phase-modulating liquid-crystal devices and examine their limitations (in terms of phase quantisation, alignment tolerances, and nonlinear response) for the encryption of 2D and 3D data. Finally, we highlight the practical importance of a highly controlled discretisation (optimal quantisation) for compression of digital holograms.

In digital holographic microscopy, shot noise is an intrinsic part of the recording process with a digital camera. We present a study based on simulations describing how shot noise influences the quality of the reconstructed phase images under different beams intensities configurations. A model for image quality estimation based on the decision statistical theory proposed by Wagner and Brown (R.F. Wagner and D.G. Brown, "Unified SNR Analysis of Medical Imaging-Systems," Phys. Med. Biol. 30, 489-518 (1985)) will be presented. A simulation will depict the variations of the reconstructed phase images SNR for different distributions of the total intensity between the reference and the object beam.

In this work we analyse the complex amplitude response of volume holograms. This analysis suggests a new scheme for encoding complex amplitude wavefront information onto an optical hologram which may prove useful for combining computer-generated holograms (CGH) onto volume holograms. Specifically, we analyse the amplitude and phase modulation associated with a volume phase unslanted transmission grating. Using the expressions given by the Kogelnik's coupled wave theory (KCWT) we find that there is a coupling between the amplitude and the phase modulations. This coupling can be controlled to some extent by means of the reconstruction angle: we have found that the significant magnitude is the normalized Bragg detune angle. A large variation range of the grating strength is desirable, which is enhanced by the use of shorter wavelengths, and materials exhibiting overmodulation capability and/or with a high thickness.

Digital holography is greatly extending the range of holography's applications and moving it from the lab into the field: a single CCD or other solid-state sensor can capture any number of holograms while numerical reconstruction within a computer eliminates the need for chemical development and readily allows further processing and visualisation of the holographic image. The steady increase in sensor pixel count leads to the possibilities of larger sample volumes, while smaller-area pixels enable the practical use of digital off-axis holography. However this increase in pixel count also drives a corresponding expansion of the computational effort needed to numerically reconstruct such holograms to an extent where the reconstruction process for a single depth slice takes significantly longer than the capture process for each single hologram. Grid computing - arecent innovation in large-scale distributed processing - provides a convenient means of harnessing significant computing resources in an ad-hoc fashion that might match the field deployment of a holographic instrument. We describe here the reconstruction of digital holograms on a trans-national computational Grid with over 10 000 nodes available at over 100 sites. A simplistic scheme of deployment was found to provide no computational advantage over a single powerful workstation. Based on these experiences we suggest an improved strategy for workflow and job execution for the replay of digital holograms on a Grid.

Liquid crystal panels, originally designed and fabricated for projection systems, are used as spatial light modulator in optical correlators or in fringe projection systems. An adapted driver electronics and measurements of the phase modulation behavior can lead to a dynamical phase modulating system with an almost linear modulation and a maximum phase shift of 2π. We built up a system with a LCD based spatial light modulator in order to realize the optical the reconstruction of digital holograms. Hologram reconstructions and the use of holographic interferograms for deformation detection are presented and future developments and applications are discussed.

Computation of the diffraction pattern that gives the desired reconstruction of an object upon proper illumination is an important process in computer generated holography. A fast computational method, based on the plane wave decomposition of 3D field in free-space, is presented to find the desired diffraction pattern. The computational burden includes two FFT algorithms in addition to a shuffling of the frequency components that needs an interpolation in the frequency domain. The algorithm is based on the exact diffraction formulation; there is no need for Fresnel or Fraunhofer approximations. The developed model is utilized to calculate the scalar optical diffraction between tilted planes for monochromatic light. The performance of the presented algorithm is satisfactory for tilt angles up to 60°.

An exact analysis of the scalar coherent monochromatic light field produced by a deflectable mirror array device is presented. The three-dimensional light field is related to the tilt angles of the mirrors. The first Rayleigh-Sommerfeld diffraction formula is used to model the diffraction. The analysis is carried out based on the assumption that the mirrors can be tilted with continuously varying angles, so the field produced by a finite (discrete) set of possible tilt angles is included as a special case.

Digital holography can record fully complex-amplitude information in a Fourier-transformed hologram between a reference and multiple-target objects. Complex amplitude of a hologram can be measured by using six-step phase-shifting interferometry with a wavelength-tuned laser diode in a Mach-Zehnder interferometer. The six-step algorithm is inherently insensitive to a laser-diode power change associated with its current variation. The correlation signal is periodically repeated by the sampled digital hologram and high-order harmonics are mixed up with the peaks corresponding to other orders. The artifact false signals can be diminished when the objects are equally dispersedly placed those separations are equal to the number of multiple objects. The experimental results are shown.

Optical holography, typically, uses laser light as coherent source for interference pattern construction and holographic registration. Interference simulation and pattern printing has been possible through computer aids and plotter printing with photographic reduction. With powerful computers and modem laser printers, computer generated holograms can be demonstrated in a simpler way. During this work, computer software was developed and Fourier holograms were produced from simple digital images. The computation process uses a Fourier Transform algorithm to simulate the interference pattern, which is then transformed into a binary matrix. The software was developed to generate also dynamic holograms from an array of digital movie frames. In this paper the software will be presented and the visualization setup and some results will be analysed.

This paper discusses the necessities for holograms to be generated in realtime for both telecommunications and video applications. Implications for implementing a fixed-point version of Direct Binary Search (DBS) in silicon studied, along with a more detailed look at the implementation and results collected for a realtime DBS method in a Field Programmable Gate Array (FPGA). The paper looks forward to future architectures and makes suggestions based on the trend of capabilities of FPGAs.

This paper presents a numerical method for processing the fringes obtained when two waves, with a quadratic phase difference function, interfere. As a particular case of this kind of fringes are the Newton's rings. The numerical method we present is based on the discrete Fresnel (Fourier) transform of the data and it has the same precision as the least square fitting (LSF).

A technique of imaging with a spatial coherence function, referred to as coherence holography, is proposed. A hologram of a three-dimensional object is recorded with coherent light in the same manner as in conventional holography, but the hologram is illuminated with spatially incoherent light to reconstruct the object as the three-dimensional distribution of a spatial coherence function, rather than as the amplitude or the intensity distribution of the optical field. A simple optical geometry for direct visualization of the reconstructed coherence image is proposed, and the results of preliminary experiments of a computer-generated coherence hologram (CGCH) are presented, which demonstrate the potential of CGCH as a means for optical coherence tomography and profilometry.

We have developed an ultrafast imaging system to record and observe the propagation of femtosecond light pulses in space and time as form of frameless motion picture. To obtain the motion picture, light-in-flight recording of holography using femtosecond pulsed laser is applied. We observed a propagating femtosecond light pulse through a dispersion prism and light pulse train generated from the integrated array illuminator. The temporal and spatial behavior of such ultrashort light pulse in the prism and from the array illuminator is clearly observed. We also demonstrate the propagation of the light pulse through scattering media in three dimensional space. The observed image of the propagating light pulse in the motion picture is different from the actual propagating pulses in shape and velocity. This is common for the light-in-flight recording of holography. These characteristics of the observed image are described.

In a two-beam interference experiment involving at least one speckle wave, intensity and phase are rapidly fluctuating distributions. There is no way to make a prediction of the evolution of the interference pattern aver distances greater than the correlation volume - as small as 3×3×100 μm³ for visible wavelengths and usual apertures. Most of the difficulties associated with a correct understanding and a good practice of speckle interferometry (SI) arise from this observation. It also explains why a technique simply ruled by the elementary two-beam interference or triangle formula raises nonetheless many problems. This contribution reviews some of the fundamentals of SI, mainly those concerned with the consequences of the random nature of the speckle phenomenon. It discusses what is thought to be the most interesting optical arrangements, modi operandi and phase extraction schemes, and finally presents selected applications. Constantly kept in mind is the idea to try to cope with the apparent disorder of the analyzed speckle distributions.

Holography is a well-known optical technique which can provide valuable information on the location and distribution of small particles in three-dimensional space. For several years now, we have utilised holography for high-precision subsea inspection and measurement. One specific application which spurred much of our work was the need for high-precision inspection and analysis of plankton sizes, distribution and species identification. To this end we have developed a subsea holographic camera (HoloMar) for recording of plankton and other marine organisms in situ in their natural environment. This camera is unique in that it is able to record simultaneous in-line and off-axis holograms to cover a range of size of marine organisms from a few microns to tens of millimetres and at concentrations from a few particles per cubic centimetre to dense aggregates. Holograms of aquatic systems of up to 50000 cm³ volume (off-axis) and 9500 cm³ (in-line), have been recorded in situ, using a pulsed laser (Q-switched, frequency-doubled Nd-YAG, 532 nm). The use of a pulsed laser effectively "freezes" the scene at a given instant. Although the recording of the holograms takes place in water, replay of the image is carried out in the laboratory in air, using the projected (real) image mode of reconstruction. By precision translation of a computer-controlled video-camera through the replayed image volume and performing "optical sectioning" on the image, individual organisms can be isolated and their size, shape and relative location precisely determined. Image processing algorithms, will allow optimisation of the holographic image together with automated identification of individual species and enumeration of concentrations. The local interactions between different organisms and particles can be observed, recorded and quantitatively determined. Following initial laboratory and observation tank testing, the holo-camera was deployed in a sea loch in the West of Scotland to a depth of 100 m and over 300 holograms recorded. However, the HoloMar camera is physically large and heavy and difficult to deploy. It is also based on the use of photographic emulsions to record the holograms. To overcome some of these difficulties we are now developing a new holographic camera (eHoloCam) based on digital holography. In digital or "eHolography", a hologram is directly electronically recorded onto a CCD or CMOS sensor and then numerically reconstructed by simulation of the optical hologram reconstruction. The immediate advantages of this new camera are compactness, ease-of-use and speed of response, but at the expense of restricted off-axis recording angles and reduced recording volume. In this paper we describe both approaches, the use of holography for analysis of marine organisms and the results obtained in the field. We also describe recent work, using both photo and digital holography, to study the behaviour of sediments in river estuaries and outline future applications of underwater holography.

The first methods for recording color holograms were established in the early 1960s. Leith and Upatnieks proposed multicolor wavefront reconstmction and Denisyuk introduced the single-beam reflection holography technique which is most suitable for recording color holograms today. Reviewed is the history of color holography highlighting important milestones. The current state-of-the-art of color holography is presented including the recording techniques using red, green and blue laser wavelengths. The laser wavelength selection issue is presented using computer simulation, showing that more than three wavelengths may be needed for accurate color rendition in holograms. The recording material is a key factor very important for creating high-quality color holograms. Covered are both the demand on the material and suitable products currently on the market. The future of color holography is highly dependent on the availability of improved panchromatic recording materials and suitable light sources for displaying the holograms. Small laser diodes as well as powerful white LEDs and OLEDs with very limited source diameters are important for color holography to become an important 3D display medium.

The subject matter of this presentation is to review the results of a research program whose objective is the development of a technology for the serial manufacturing of high efficiency HOE (Holographic Optical Elements) with predetermined spectral characteristics and angular selectivity with apertures ranging from few square millimeters to square meters. The developed technology includes the machine fabrication of precision holographic films (2 to 50 micron thickness) on glass or plastic substrata and chemically and thermally adapted hologram development processes. The desired optical properties of the holographic material for a specific technical application are preset during the making of the film and are modified during the exposure and the development of the HOE.

Methods for recording of holograms with an encoded hidden image (security holograms) and a reading-decoding optoelectronic system are presented in this paper. Security holograms are used as means for control of authenticity of the protected objects. Some modifications of the recording schemes with the code mask in the object beam are proposed. The main problem to be solved is connected with the required precision of the hologram positioning in the readout device. The algorithm of reconstruction of the decoded image is proposed in this paper. The main feature of this algorithm is the presence of the optical and electronic decoding. It allows producing of better than previously protected holograms. As an additional measure of protection of the hologram it is proposed to use the predetermined elements of the hidden image for checking of the hologram authenticity.

A holographic sight permits fast choice of the aiming sign in a variety of environmental conditions. The aiming sign, the target and the place are observed simultaneously. The aiming mark doesn't require accommodation of the eyes. Position of the aiming mark in the target plane provides the shooting at the stacking of the aiming mark to the target independently on observing angle and position of the shooting. Second advantage of holographic sight is hiding of the shooter. In this paper, a design of the optical scheme for parallax control of the holographic optical element (HOE) and the holographic sight with HOE is discussed. A solution for the removal of the aiming sign parallax has been proposed. The parallax is defined as non-coincidence of the target plane and plane of the aiming sign and depends on the aberrations of the holographic optical element.

The DOE-HOE's, made by Dot-matrix technology, have found application in various areas, such as security, protection of various goods from faking, packing etc. These holograms contain a set of pixels with diffraction gratings with different spatial frequencies and orientation. The process of manufacturing represents a consecutive pixels exposure. The pixels quantity is great (about 10⁵-10⁶), that's why master-shim manufacturing requires considerable time. Spatial frequency and orientation of gratings change because of mechanical shift of elements. For acceleration of the recording process it is necessary to replace slow mechanical devices with high-speed ones. This paper proposes a possible solution of this problem, by using a spatial light modulator. This paper describes the technique and results of calculations of optical components parameters.

Three electronic speckle pattern shearing interferometers (ESPSI) using photopolymer holographic gratings to produce the sheared image are presented. In the first ESPSI system two holographic gratings are used. The gratings are placed between the object and an imaging lens in front of the CCD camera. In the second ESPSI system one grating is used in combination with a sheet of ground glass. The sheared images on the ground glass are further imaged onto a CCD camera. In the third ESPSI system only one grating is used - it is placed in front of the object. The image and the sheared image are imaged onto the CCD camera, whose optical axis coincides with the normal to the object surface. The introduction of photopolymer holographic gratings in ESPSI systems gives the advantage of using high aperture optical elements at relatively low price. The systems are compared in terms of flexibility in their adjustment, sensitivity, suitability and limitations for different applications.

A transform-domain fringe pattern denoising technique is presented. The Discrete Cosine Transform (DCT) is applied in a sliding window manner to get an overcomplete image expansion, and then the transform coefficients are thresholded to reduce the noise. We investigate the proper size of the sliding window and the proper threshold level. The latter is determined individually for each window position using a local noise variance estimate. In order to deal with a rather inadequate but simplified noise model, a proportionality factor, related with the speckle size, is found by experiments with digitally simulated speckle fringes. Such a proportionality factor suggests that the technique could be made fully automatic. We demonstrate promising results in denoising of real speckle fringe patterns, obtained through an out-of-plane sensitive Digital Speckle Pattern Interferometry (DSPI) set-up in a process of non-destructive testing of reinforced composite materials deformation.

An interferometric method, called digital multispectral holography, to obtain three-dimensional (3D) multispectral images of spatially incoherent, polychromatic source distributions is presented. Each 3D spectral image is retrieved separately from a 3D spatial coherence function that is synthesized from interferograms measured with a two-axes wavefront folding interferometer. Numerical demonstration incorporated with spatially extended polychromatic source distribution, located at nearfield positions, shows that the 3D information of each spectral component is successfully retrieved by the method.

Fringes projection and speckle shear interferometry are used for testing of subjected to cycling loading (pressure) composite vessel. As the sensitivity of the applied methods could vary in broad limits in comparison with the other interferometric techniques, the inspection is realized in a wide dynamic range. Two spacing phase stepping fringes projection interferometry is applied for absolute coordinate measurement. Derivatives of in-plane and out-of-the-plane components of the displacement vector over the object surface are obtained by lateral speckle shear interferometry in static loading (pressure). Non-linear mechanical response and fatigue of composite material are clearly detected after cyclic sinusoidal loading by macro measurement using lateral speckle shear interferometry. Fringes projection and speckle-shear interferometry are suitable for shape and normal displacements measurements in a wider dynamic range. The other advantage of the shown methods is connected with the possibility to realize compact and portable devices for in-situ inspection of investigated objects - machine parts and constructions.

A two-spacing phase-shifting techniques for three-dimensional shape measurement based on digital fringe projection is presented. Combination of phase-shifting method with computer generated fringe patterns with a sinusoidal intensity profile allows precise measurement in real time operating mode. The two-spacing technique allows absolute coordinate estimation of the investigated specimen. The theoretical background, experimental results as well as comparison with traditional laser phase-shifting interferometry are discussed. The obtained outcomes successfully display the applicability of this technique for surface profile measurement. The proposed technique is especially useful for remote, non-destructive in-situ inspection of real objects.

The inverse source problem is solved by utilization of reverse Fourier transformation of the light, transmitted through the object. Phase-shifting technique for obtaining the information on the phase distribution during measurement is proposed. This allows calculation of the transmission coefficient and phase delay in every point of the object. The incorporation of a reference measurement eliminates the influence of the measurement system parameters. The theoretical background is shown. A computer simulation of the influence of the more important factors of the optical scheme on the accuracy is presented. Simulation is done for different positions of the basic optical elements and inexact phase shifting. Different ADC resolutions are simulated too. Conditions and limits of measurement are discussed. This technique could be used in measurement and qualification of small and micro objects in biology.

A broadband laser-based technique for investigation the parameters of spectral selectivity high-selective volume hologram is suggested. The studies, carried out by this method, were realized with using radiation of femtosecond and semiconductor lasers. The transmission phase holographic gratings recorded on polymer recording media samples of 1-2 mm thickness were used. The results of investigations of spectral selectivity of transmission phase holographic gratings of various frequencies are presented. The verification of obtained results was fulfilled. The limits of technique validity were estimated.

The problem of predicting and previsualizing the distortions and aberrations in a holographic image is discussed, particularly for the case of pictorial, or display holograms. The mathematical procedure for predicting these attributes is outlined, followed by a brief outline of a computer program (HoloPov), written in the POV-Ray language, that can be used both to calculate these attributes and to display them. A brief outline is also given of a graphical user interface produced to allow fast manipulation of input data.

In this paper, we present a transmission polarization digital holographic microscope (Pol-DHM) that allows for imaging the state of polarization of a wave front with the acquisition of a single hologram. This apparatus records, using a CCD camera, the interference in off-axis geometry between two orthogonally polarized reference waves and an object wave transmitted through a microscopic sample and magnified by a microscope objective. Since the reference waves have orthogonal polarizations, they do not interfere and the hologram results in two different fringes patterns, which can be separately filtered in the spatial Fourier domain and reconstructed separately to compute the amplitude and phase of two wave fronts. These four images allow computing the polarization ellipse azimuth and the phase difference associated with the polarization state of the object wave. The method is illustrated by imaging the strain induced in a polymethylmethacrylate (PMMA) sample and in a bended optical fiber.

Results are presented of holographic investigations of current sheets formed in 3D magnetic fields with X lines. The experimental plasma device, optical scheme of holographic interferograms recording and interpretation are considered. The influence of the guide field B_z on the dynamics and structure of the current sheets was investigated. Asymmetry and tilting the current sheets formed in the plasmas of heavy noble gases were observed and interpreted as a manifestation of two-fluid properties of plasmas with heavy ions.

Great improvement of CuBr laser beam spatial coherence was made by a special design of the laser resonator, the generalized diffraction filtered resonator. Utilizing it diffraction-limited beam divergence can be easily obtained throughout the laser pulse. Since the spatial coherence is in inverse relation with the beam divergence, decreasing the latter we increase the former. The temporal evolution of beam divergence for the more intense green (λ=510nm) laser line was measured within laser pulse of MO (master oscillator) CuBr laser system fitted with a stable plane-plane resonator (PPR), a confocal unstable resonator of positive branch (PBUR) and a generalized diffraction filtered resonator (GDFR). With the MOPA (master oscillator power amplifier) system only GDFR was used. The estimations were verified by direct coherence measurements by means of a reversal shear interferometer that was a modified Michelson interferometer. The estimations as well as the direct measurement of spatial coherence show that coherence degree increases from PPR through PBUR to GDFR. Moreover, with GDFR it is time-independent. With MOPA system the coherence degree goes up further. So the degree of coherence measured interferometrically with MO is: for PPR - 0.16, for PBUR - 0.28 and for GDFR - 0.36. For MOPA the measured degree of coherence reaches 0.65. The estimated and the measured coherence trends show similarity. Based on the Michelson interferometer and having just four optical components (a spherical lens, an optical wedge and two plane mirrors), a new rigid instrument for spatial coherence analysis of optical beams was introduced as well.

Recently, Ebbesen et al. (Nature v.391, p.667, 1998), have reported an 'extraordinary optical transmission' (EOT) enhancement of several orders of magnitude in thin metallic films with perforated circular subwavelength holes. Later, it was shown that this phenomenon does not require the existence of apertures. Continuous thin metal films with constant thickness give a similar EOT, provided they are 1D or 2D modulated. Still there is no detailed understanding of the physical nature of this transmission enhancement. It could be explained by plasmon-polariton interactions; yet another hypothesis suggests that it occurs from waveguide mode resonance. In this communication, we report experimental data on the optical response of a simple 1D relief grating structure with EOT. We have studied the transmission wavelength dependence as well as the angular dispersion of the grating reflection. Our experimental results are consistent with the involvement of p-polarized resonant modes.

Holographic gratings recorded in polymer-dispersed liquid crystals (H-PDLC) are very interesting as systems for electrically switchable diffractive devices. From the early 1990s, experiments, Bragg and Raman-Nath gratings are recorded in PDLC. A very thorough review of these investigations is published recently. In this paper we report our first experiments for H-PDLC gratings, recorded in two different optical arrangements using total internal reflection (TIR): 1) Stetson's scheme - when low and high spatial frequencies gratings are simultaneously recorded in the PDLC's volume, and 2) Nassenstein's scheme - when low or high spatial frequency grating is recorded with evanescent waves in very thin layer of the PDLC. A polarization grating recorded by the Stetson's scheme is also reported. The realtime diffraction efficiency dependence during the recording and the polarization characteristics are investigated.

The schemes of degenerate and nondegenerate multiwave mixing in saturable absorbers (Rhodamine 6G and polymethine 3274 U dyes) exhibiting higher-order nonlinearities have been analyzed experimentally. The role of polarization gratings resultant from spatial modulation of the light field polarization state at the orthogonal polarization of the hologram recording waves has been established. Also, it has been found that polarization of the diffracted wave is dependent on the diffraction order. The frequency conversion of coherent images from infrared to the visible and between different wavelengths of the visible region has been realized experimentally.

The schemes for nonlinear recording of dynamic holograms in multilevel resonant media, in conditions when the fifth- and higher-order nonlinearities are exhibited, have been studied both theoretically and experimentally. The optical methods to control the diffraction efficiency of nonlinear dynamic holograms with the use of an additional light beam tuned out into the absorption band from the ground or excited state of the molecules have been considered.

Intensity and pure polarization holographic gratings in silica-based sol-gel thin films, containing carbazole group and Disperse Red 1, are obtained by photoisomerization at 488 nm and are investigated by means of the moving grating technique (MGT). General equations relating the modulated MGT signal to amplitudes and phase shifts of the index and absorption gratings are derived for thin films in the case of different polarization configurations. It is shown that the technique, commonly used to characterize photorefractive gratings, is a powerful tool to investigate the orientation mechanisms responsible for the holographic polarization gratings formation.