A novel photopolymer system, which is capable of producing high diffraction efficiency in volume phase holograms, is reported. This photopolymer system consists primarily of bisphenol-type epoxy resin and radically polymerizable aliphatic monomer with diphenyliodonium salt and 3,3'-carbonylbis (7-diethylaminocoumarin) as a complex initiator. The chemistry of imaging formation is based on the radical polymerization of the monomer initiated by a holographic exposure, followed by the cationic polymerization of epoxy resin by heat treatment. Then, radical species and cations are provided through a photocomposition of diphenyliodonium salt.

Photoactive polymer matrices are investigated by and for holographic recording at 514 nm. The photopolymers are based on acrylamide monomers, which are dissolved together with xanthine dyes and other additives in polyvinylalcohol. Dry plastic coatings are obtained by casting the aqueous polymer solutions on glass substrates. Photorecording occurs in real-time and in-situ, without any post-exposure processing. This paper describes the influences of chemical additives on the photorecording process. Specifically, the addition of diphenyl iodonium chloride (DPI-Cl), in conjunction with triethanolamine (TEA), significantly increases the exposure sensitivities, by a factor of over three (to about 15 mJ/cm²). This sensitizing effect is shown to originate from a superadditive effect between TEA and DPI-Cl. The mechanism of the superadditive effect is discussed by a proposed reaction model. The exposure sensitivities are also significantly influenced by the PVA binder parameters, such as average molecular weights and degree of hydrolization. The present formulations produce large enough refractive index modulations, so that very high diffraction efficiencies (DEs > 90%) are obtained. The dynamic range of refractive index modulations was increased from 0.014 to 0.018 by the addition of glutaraldehyde crosslinking, which also improves the dimensional stability of the holograms.

Work done on the optimization of a photopolymer holographic recording material is presented. The material consists of a PVA (polyvinylalcohol) binder, a monomer, a crosslinking monomer, an electron donor and a dye sensitizer which renders the material suitable for recording in the 633 nm spectral region. Diffraction gratings were recorded with approximately 80% diffraction efficiency with the optimized system. By changing the relative concentrations of the components in the material, sensitivity was improved by a factor of 5. Total light power remained at approximately 5.5 mW for recording.

In this paper, a novel photoetching cellulose film is presented. The basic photochemical reaction process and the mechanism of image formation is discussed by means of electron spin resonance spectra and infrared spectra. Meanwhile, its characteristics such as stronger real- time effect, higher spatial resolution, linear surface relief modulation capacity and delay development effect are investigated experimentally.

Results of experiments on synthesis of a thick-layered light-sensitive material on the base of gel-like dichromated gelatin are presented. In these experiments, the coated layer of liquid dichromated was not subjected to drying but it was sealed between two glasses in order to be protected from drying. The recording was performed on moisture-saturated layers after the liquid was transformed into gel. The thickness of the layer varied from 1 to 3 mm. The maximum efficiency of transmission holograms recorded in the layer reached 17%. The sensitivity to the blue light ((lambda) equals 0.44 micrometers ) was about 10 J/cm².

The photoinduced reversible color change between thermally stable and meta stable states of spiropyran molecules can modulate the absorption and the refractive index of the photochromic doped poly(vinylcarbazole) films. The effect of the exposure energy and the film thickness on the real-time diffraction efficiency was investigated. The optimal thickness for which the maximum diffraction efficiency is obtained was found to be around 30 micrometers for an exposure energy greater than 1005 mJ/cm². High efficiency erasable holographic recording at 350 nm was performed. A maximum diffraction efficiency of 13% was achieved for spiropyran doped poly(vinylcarbazole) films.

Photochromic dyes like the fulgides `Aberchrome 540' and `Aberchrome 670' have been investigated in the polymer films with respect to the formation of holographic gratings. For high exposure doses the diffraction efficiencies tend to decrease with additional exposure. This is discussed in terms of nonlinear gratings due to the photochromic mechanism in a 2 level model. Two methods for the fabrication of latent photochromic gratings, which can be switched on by a homogeneous noncoherent exposure are discussed.

Azo-dye doped polymer (ADP) systems have shown to be remarkable photosensitive media for holographic recording and optical computing. The totally reversible trans-cis photoionization mechanism induced by actinic light allows the real-time recording of phase holograms on the doped polymer matrices. These ADP systems can also be used to perform polarization holography as they present the Weigert effect. Real-time operations such as contrast reversal, optical demultiplexing, addition and subtraction of two overlapping cross-polarized signals have been performed successfully.

Nonlinear refraction of a new polymer structure based upon diglycidylether of bisphenol-A has been studied in connection with transient holographic grating recording. The polymer contains 4 aminoazobensen as nonlinear optically active side groups covalently attached at each monomer unit. Dynamic grating writing and relaxation processes have been studied using frequency doubled YAG:Nd⁺³ laser ((tau) _p equals 20 ns, (lambda) equals 0.53 micrometers ). The dynamics of transient gratings was shown to have two different erasure times corresponding to different nonlinearity mechanisms fast one (relaxation time 20 ns and (chi) ⁽³) equals 5 (DOT) 10^-8 esu) and slow one (quasi-stationary). The later makes it possible to write and erase phase gratings reversibly by ns pulses and store information for hours. An analysis of possible mechanisms for refractive index nonlinear behavior in new structure is presented. In particular, a role of TRANS-CIS photoisomerization of the azo-compound in nonlinear optical properties of the structure is discussed. The results vividly manifest the possibility of the polymer to be used as reversible medium for information storage. Besides, the polymer structure in question exhibits both ns and quasistationary response together with simplicity of fabrication and low prises which have wide prospects for different applications in the field of optical data processing.

The results of investigations of real-time gratings recording in lightsensitive medium of photosynthetic reaction centers that have absorption bands in near IR are presented. Investigations were carried out using low-intensity semiconductor lasers of different wavelengths. The contribution of absorption and dispersive components to grating is evaluated. The maximum diffraction efficiency value was 0.05%. The spatial-frequency dependence of grating efficiency is investigated.

The Lippmann photographic process relied on very fine grain silver halide emulsions with panchromatic spectral sensitizers. Emulsions for this process have not been commercially available since around the turn of the century. Recent availability of suitable Russian silver halide emulsions (PFG-03c) from Slavich Company made revisiting this process possible. Experimentation with these plates resulted in full color spectrums and outdoor still life photographs that gave a basis for further investigation of making laboratory silver halide emulsions. This paper will present procedures and results for the making of Lippmann photographs from silver halide emulsions and from other recording materials.

The recording of holograms in which the reference beam enters through the supporting substrate involves attenuation factors which differ strongly between signal and reference. This paper addresses the issue of fringe contrast under these extreme conditions and provides quantitative data that are indicative of at least a partial solution to the problem. We define a spatial average for the fringe contrast and offer results which follow our theoretical model for Du Pont OmniDex^TM photopolymers. The direct edge referenced technique for recording is re-visited with observation of a new phenomenon which we call self-induced index matching. An alternative fringe recording geometry is proposed and compared with direct recording.

A technique is described for determining three-color exposure energies to achieve a specific color balance in multicolor holographic recordings. The technique relies on the application of multivariable analysis to a series of exposures in which the intensity of the three recording colors is varied. Modeling required for the technique is discussed, followed by examples of three-color holographic mirrors exposed simultaneously in experimental full-color photopolymer film.

Photopolymers can be considered viable holographic material because of their many attractive features. Among these we could mention their ability to self-develop, the fact dry processing can be used with them, their good stability and thick emulsion layers, their haigh sensitivity, diffraction efficiency and resolution, and finally their non-volatile storage. Among the different sources of noise in holography, noise gratings are due to scattering from inhomogeneities in the recording material and have an important spurious effect on volume holography. Their effect at reconstruction is to bring about a reduction in diffraction efficiency and signal-to-noise ratio. Even though these scatter gratings have been seen in PMMA and other photopolymers, and in photorefractive crystals, they have really only been analyzed extensively for photographic emulsions, and information about these grating structures in photopolymers is quite scarce. In this communication we present the observation of noise gratings in an acrylamide photopolymer for use in real time holography. The possibilities of this noise source as a optimization technique for this type of materials are pointed out. Noise gratings in these polymer films were created upon exposure to a He-Ne laser collimated beam at 633 nm without any subsequent processing step. The influence of intensity on recording noise gratings and angular selectivity are reported showing its influence on the recording of this type of noise source in real time holographic materials.

We report an experimental study of the use of DuPont photopolymer Holographic Recording Film (HRF) to record high resolution reflection holograms. The goals of this work are to investigate techniques for recording images of the 3D surfaces of objects, such as integrated circuit chips, without the use of imaging optics and step and repeat techniques, and to investigate techniques for reconstructing these images through a conventional or slightly modified optical microscope. We use the Denisyuk reflection geometry to record single wavelength and multiple wavelength contact-copy and near-contact holograms of an integrated circuit chip. We present photographs of the holographic reconstructions as generated and viewed through a conventional microscope. The images demonstrate color contrast and clearly resolved features of less than 1 micron. In addition, we present an experimental investigation and theoretical modeling of the grating formation process in the DuPont photopolymer HRF. Experiments are described which measure the real-time growth and accompanying real-time shrinkage of reflection gratings. A theory is outlined that includes coupling of the writing beams with the real time growth and shrinkage of nonuniform gratings throughout the thickness of the recording emulsion. Results are presented for three types of DuPont photopolymer HRF.

Using of an improved developer with optical latensification allowed to significantly increase exposure sensitivity of currently in use silver halide materials. Transmission large-scale holograms (30 X 40 cm²) of diffused objects have been recorded under pulse exposure of about 6.5 X 10^-6 J/cm² for VRP and of about 2 X 10^-6 J/cm² for Agfa-Gavaert 8E56HD, in both cases without appreciable contrast deterioration. Results of the first experiments on pulse reflection holography are also discussed.

Holographic nonspatial filters designed to clean up the output of a laser have been shown to be a great improvement over conventional spatial filters. This paper successfully addresses several major problems or shortcomings of the nonspatial filter. The problems were in the use of two filters together for cleaning up a laser beam in both dimensions. Polarization and orientation effects made the system complicated an inconvenient. A simple compound element consisting of a sandwich of two identical holograms is shown to solve these problems.